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ip22zilog.c

/*
 * Driver for Zilog serial chips found on SGI workstations and
 * servers.  This driver could actually be made more generic.
 *
 * This is based on the drivers/serial/sunzilog.c code as of 2.6.0-test7 and the
 * old drivers/sgi/char/sgiserial.c code which itself is based of the original
 * drivers/sbus/char/zs.c code.  A lot of code has been simply moved over
 * directly from there but much has been rewritten.  Credits therefore go out
 * to David S. Miller, Eddie C. Dost, Pete Zaitcev, Ted Ts'o and Alex Buell
 * for their work there.
 *
 *  Copyright (C) 2002 Ralf Baechle (ralf@linux-mips.org)
 *  Copyright (C) 2002 David S. Miller (davem@redhat.com)
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/circ_buf.h>
#include <linux/serial.h>
#include <linux/sysrq.h>
#include <linux/console.h>
#include <linux/spinlock.h>
#include <linux/init.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/sgialib.h>
#include <asm/sgi/ioc.h>
#include <asm/sgi/hpc3.h>
#include <asm/sgi/ip22.h>

#if defined(CONFIG_SERIAL_IP22_ZILOG_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#include "ip22zilog.h"

/*
 * On IP22 we need to delay after register accesses but we do not need to
 * flush writes.
 */
#define ZSDELAY()       udelay(5)
#define ZSDELAY_LONG()        udelay(20)
#define ZS_WSYNC(channel)     do { } while (0)

#define NUM_IP22ZILOG         1
#define NUM_CHANNELS          (NUM_IP22ZILOG * 2)

#define ZS_CLOCK        3672000     /* Zilog input clock rate. */
#define ZS_CLOCK_DIVISOR      16      /* Divisor this driver uses. */

/*
 * We wrap our port structure around the generic uart_port.
 */
struct uart_ip22zilog_port {
      struct uart_port        port;

      /* IRQ servicing chain.  */
      struct uart_ip22zilog_port    *next;

      /* Current values of Zilog write registers.  */
      unsigned char                 curregs[NUM_ZSREGS];

      unsigned int                  flags;
#define IP22ZILOG_FLAG_IS_CONS            0x00000004
#define IP22ZILOG_FLAG_IS_KGDB            0x00000008
#define IP22ZILOG_FLAG_MODEM_STATUS 0x00000010
#define IP22ZILOG_FLAG_IS_CHANNEL_A 0x00000020
#define IP22ZILOG_FLAG_REGS_HELD    0x00000040
#define IP22ZILOG_FLAG_TX_STOPPED   0x00000080
#define IP22ZILOG_FLAG_TX_ACTIVE    0x00000100
#define IP22ZILOG_FLAG_RESET_DONE   0x00000200

      unsigned int                  tty_break;

      unsigned char                 parity_mask;
      unsigned char                 prev_status;
};

#define ZILOG_CHANNEL_FROM_PORT(PORT)     ((struct zilog_channel *)((PORT)->membase))
#define UART_ZILOG(PORT)            ((struct uart_ip22zilog_port *)(PORT))
#define IP22ZILOG_GET_CURR_REG(PORT, REGNUM)          \
      (UART_ZILOG(PORT)->curregs[REGNUM])
#define IP22ZILOG_SET_CURR_REG(PORT, REGNUM, REGVAL)  \
      ((UART_ZILOG(PORT)->curregs[REGNUM]) = (REGVAL))
#define ZS_IS_CONS(UP)  ((UP)->flags & IP22ZILOG_FLAG_IS_CONS)
#define ZS_IS_KGDB(UP)  ((UP)->flags & IP22ZILOG_FLAG_IS_KGDB)
#define ZS_WANTS_MODEM_STATUS(UP)   ((UP)->flags & IP22ZILOG_FLAG_MODEM_STATUS)
#define ZS_IS_CHANNEL_A(UP)   ((UP)->flags & IP22ZILOG_FLAG_IS_CHANNEL_A)
#define ZS_REGS_HELD(UP)      ((UP)->flags & IP22ZILOG_FLAG_REGS_HELD)
#define ZS_TX_STOPPED(UP)     ((UP)->flags & IP22ZILOG_FLAG_TX_STOPPED)
#define ZS_TX_ACTIVE(UP)      ((UP)->flags & IP22ZILOG_FLAG_TX_ACTIVE)

/* Reading and writing Zilog8530 registers.  The delays are to make this
 * driver work on the IP22 which needs a settling delay after each chip
 * register access, other machines handle this in hardware via auxiliary
 * flip-flops which implement the settle time we do in software.
 *
 * The port lock must be held and local IRQs must be disabled
 * when {read,write}_zsreg is invoked.
 */
static unsigned char read_zsreg(struct zilog_channel *channel,
                        unsigned char reg)
{
      unsigned char retval;

      writeb(reg, &channel->control);
      ZSDELAY();
      retval = readb(&channel->control);
      ZSDELAY();

      return retval;
}

static void write_zsreg(struct zilog_channel *channel,
                  unsigned char reg, unsigned char value)
{
      writeb(reg, &channel->control);
      ZSDELAY();
      writeb(value, &channel->control);
      ZSDELAY();
}

static void ip22zilog_clear_fifo(struct zilog_channel *channel)
{
      int i;

      for (i = 0; i < 32; i++) {
            unsigned char regval;

            regval = readb(&channel->control);
            ZSDELAY();
            if (regval & Rx_CH_AV)
                  break;

            regval = read_zsreg(channel, R1);
            readb(&channel->data);
            ZSDELAY();

            if (regval & (PAR_ERR | Rx_OVR | CRC_ERR)) {
                  writeb(ERR_RES, &channel->control);
                  ZSDELAY();
                  ZS_WSYNC(channel);
            }
      }
}

/* This function must only be called when the TX is not busy.  The UART
 * port lock must be held and local interrupts disabled.
 */
static void __load_zsregs(struct zilog_channel *channel, unsigned char *regs)
{
      int i;

      /* Let pending transmits finish.  */
      for (i = 0; i < 1000; i++) {
            unsigned char stat = read_zsreg(channel, R1);
            if (stat & ALL_SNT)
                  break;
            udelay(100);
      }

      writeb(ERR_RES, &channel->control);
      ZSDELAY();
      ZS_WSYNC(channel);

      ip22zilog_clear_fifo(channel);

      /* Disable all interrupts.  */
      write_zsreg(channel, R1,
                regs[R1] & ~(RxINT_MASK | TxINT_ENAB | EXT_INT_ENAB));

      /* Set parity, sync config, stop bits, and clock divisor.  */
      write_zsreg(channel, R4, regs[R4]);

      /* Set misc. TX/RX control bits.  */
      write_zsreg(channel, R10, regs[R10]);

      /* Set TX/RX controls sans the enable bits.  */
      write_zsreg(channel, R3, regs[R3] & ~RxENAB);
      write_zsreg(channel, R5, regs[R5] & ~TxENAB);

      /* Synchronous mode config.  */
      write_zsreg(channel, R6, regs[R6]);
      write_zsreg(channel, R7, regs[R7]);

      /* Don't mess with the interrupt vector (R2, unused by us) and
       * master interrupt control (R9).  We make sure this is setup
       * properly at probe time then never touch it again.
       */

      /* Disable baud generator.  */
      write_zsreg(channel, R14, regs[R14] & ~BRENAB);

      /* Clock mode control.  */
      write_zsreg(channel, R11, regs[R11]);

      /* Lower and upper byte of baud rate generator divisor.  */
      write_zsreg(channel, R12, regs[R12]);
      write_zsreg(channel, R13, regs[R13]);

      /* Now rewrite R14, with BRENAB (if set).  */
      write_zsreg(channel, R14, regs[R14]);

      /* External status interrupt control.  */
      write_zsreg(channel, R15, regs[R15]);

      /* Reset external status interrupts.  */
      write_zsreg(channel, R0, RES_EXT_INT);
      write_zsreg(channel, R0, RES_EXT_INT);

      /* Rewrite R3/R5, this time without enables masked.  */
      write_zsreg(channel, R3, regs[R3]);
      write_zsreg(channel, R5, regs[R5]);

      /* Rewrite R1, this time without IRQ enabled masked.  */
      write_zsreg(channel, R1, regs[R1]);
}

/* Reprogram the Zilog channel HW registers with the copies found in the
 * software state struct.  If the transmitter is busy, we defer this update
 * until the next TX complete interrupt.  Else, we do it right now.
 *
 * The UART port lock must be held and local interrupts disabled.
 */
static void ip22zilog_maybe_update_regs(struct uart_ip22zilog_port *up,
                               struct zilog_channel *channel)
{
      if (!ZS_REGS_HELD(up)) {
            if (ZS_TX_ACTIVE(up)) {
                  up->flags |= IP22ZILOG_FLAG_REGS_HELD;
            } else {
                  __load_zsregs(channel, up->curregs);
            }
      }
}

#define Rx_BRK 0x0100                   /* BREAK event software flag.  */
#define Rx_SYS 0x0200                   /* SysRq event software flag.  */

static struct tty_struct *ip22zilog_receive_chars(struct uart_ip22zilog_port *up,
                                      struct zilog_channel *channel)
{
      struct tty_struct *tty;
      unsigned char ch, flag;
      unsigned int r1;

      tty = NULL;
      if (up->port.info != NULL &&
          up->port.info->tty != NULL)
            tty = up->port.info->tty;

      for (;;) {
            ch = readb(&channel->control);
            ZSDELAY();
            if (!(ch & Rx_CH_AV))
                  break;

            r1 = read_zsreg(channel, R1);
            if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR)) {
                  writeb(ERR_RES, &channel->control);
                  ZSDELAY();
                  ZS_WSYNC(channel);
            }

            ch = readb(&channel->data);
            ZSDELAY();

            ch &= up->parity_mask;

            /* Handle the null char got when BREAK is removed.  */
            if (!ch)
                  r1 |= up->tty_break;

            /* A real serial line, record the character and status.  */
            flag = TTY_NORMAL;
            up->port.icount.rx++;
            if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR | Rx_SYS | Rx_BRK)) {
                  up->tty_break = 0;

                  if (r1 & (Rx_SYS | Rx_BRK)) {
                        up->port.icount.brk++;
                        if (r1 & Rx_SYS)
                              continue;
                        r1 &= ~(PAR_ERR | CRC_ERR);
                  }
                  else if (r1 & PAR_ERR)
                        up->port.icount.parity++;
                  else if (r1 & CRC_ERR)
                        up->port.icount.frame++;
                  if (r1 & Rx_OVR)
                        up->port.icount.overrun++;
                  r1 &= up->port.read_status_mask;
                  if (r1 & Rx_BRK)
                        flag = TTY_BREAK;
                  else if (r1 & PAR_ERR)
                        flag = TTY_PARITY;
                  else if (r1 & CRC_ERR)
                        flag = TTY_FRAME;
            }

            if (uart_handle_sysrq_char(&up->port, ch))
                  continue;

            if (tty)
                  uart_insert_char(&up->port, r1, Rx_OVR, ch, flag);
      }
      return tty;
}

static void ip22zilog_status_handle(struct uart_ip22zilog_port *up,
                           struct zilog_channel *channel)
{
      unsigned char status;

      status = readb(&channel->control);
      ZSDELAY();

      writeb(RES_EXT_INT, &channel->control);
      ZSDELAY();
      ZS_WSYNC(channel);

      if (up->curregs[R15] & BRKIE) {
            if ((status & BRK_ABRT) && !(up->prev_status & BRK_ABRT)) {
                  if (uart_handle_break(&up->port))
                        up->tty_break = Rx_SYS;
                  else
                        up->tty_break = Rx_BRK;
            }
      }

      if (ZS_WANTS_MODEM_STATUS(up)) {
            if (status & SYNC)
                  up->port.icount.dsr++;

            /* The Zilog just gives us an interrupt when DCD/CTS/etc. change.
             * But it does not tell us which bit has changed, we have to keep
             * track of this ourselves.
             */
            if ((status ^ up->prev_status) ^ DCD)
                  uart_handle_dcd_change(&up->port,
                                     (status & DCD));
            if ((status ^ up->prev_status) ^ CTS)
                  uart_handle_cts_change(&up->port,
                                     (status & CTS));

            wake_up_interruptible(&up->port.info->delta_msr_wait);
      }

      up->prev_status = status;
}

static void ip22zilog_transmit_chars(struct uart_ip22zilog_port *up,
                            struct zilog_channel *channel)
{
      struct circ_buf *xmit;

      if (ZS_IS_CONS(up)) {
            unsigned char status = readb(&channel->control);
            ZSDELAY();

            /* TX still busy?  Just wait for the next TX done interrupt.
             *
             * It can occur because of how we do serial console writes.  It would
             * be nice to transmit console writes just like we normally would for
             * a TTY line. (ie. buffered and TX interrupt driven).  That is not
             * easy because console writes cannot sleep.  One solution might be
             * to poll on enough port->xmit space becomming free.  -DaveM
             */
            if (!(status & Tx_BUF_EMP))
                  return;
      }

      up->flags &= ~IP22ZILOG_FLAG_TX_ACTIVE;

      if (ZS_REGS_HELD(up)) {
            __load_zsregs(channel, up->curregs);
            up->flags &= ~IP22ZILOG_FLAG_REGS_HELD;
      }

      if (ZS_TX_STOPPED(up)) {
            up->flags &= ~IP22ZILOG_FLAG_TX_STOPPED;
            goto ack_tx_int;
      }

      if (up->port.x_char) {
            up->flags |= IP22ZILOG_FLAG_TX_ACTIVE;
            writeb(up->port.x_char, &channel->data);
            ZSDELAY();
            ZS_WSYNC(channel);

            up->port.icount.tx++;
            up->port.x_char = 0;
            return;
      }

      if (up->port.info == NULL)
            goto ack_tx_int;
      xmit = &up->port.info->xmit;
      if (uart_circ_empty(xmit))
            goto ack_tx_int;
      if (uart_tx_stopped(&up->port))
            goto ack_tx_int;

      up->flags |= IP22ZILOG_FLAG_TX_ACTIVE;
      writeb(xmit->buf[xmit->tail], &channel->data);
      ZSDELAY();
      ZS_WSYNC(channel);

      xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
      up->port.icount.tx++;

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

      return;

ack_tx_int:
      writeb(RES_Tx_P, &channel->control);
      ZSDELAY();
      ZS_WSYNC(channel);
}

static irqreturn_t ip22zilog_interrupt(int irq, void *dev_id)
{
      struct uart_ip22zilog_port *up = dev_id;

      while (up) {
            struct zilog_channel *channel
                  = ZILOG_CHANNEL_FROM_PORT(&up->port);
            struct tty_struct *tty;
            unsigned char r3;

            spin_lock(&up->port.lock);
            r3 = read_zsreg(channel, R3);

            /* Channel A */
            tty = NULL;
            if (r3 & (CHAEXT | CHATxIP | CHARxIP)) {
                  writeb(RES_H_IUS, &channel->control);
                  ZSDELAY();
                  ZS_WSYNC(channel);

                  if (r3 & CHARxIP)
                        tty = ip22zilog_receive_chars(up, channel);
                  if (r3 & CHAEXT)
                        ip22zilog_status_handle(up, channel);
                  if (r3 & CHATxIP)
                        ip22zilog_transmit_chars(up, channel);
            }
            spin_unlock(&up->port.lock);

            if (tty)
                  tty_flip_buffer_push(tty);

            /* Channel B */
            up = up->next;
            channel = ZILOG_CHANNEL_FROM_PORT(&up->port);

            spin_lock(&up->port.lock);
            tty = NULL;
            if (r3 & (CHBEXT | CHBTxIP | CHBRxIP)) {
                  writeb(RES_H_IUS, &channel->control);
                  ZSDELAY();
                  ZS_WSYNC(channel);

                  if (r3 & CHBRxIP)
                        tty = ip22zilog_receive_chars(up, channel);
                  if (r3 & CHBEXT)
                        ip22zilog_status_handle(up, channel);
                  if (r3 & CHBTxIP)
                        ip22zilog_transmit_chars(up, channel);
            }
            spin_unlock(&up->port.lock);

            if (tty)
                  tty_flip_buffer_push(tty);

            up = up->next;
      }

      return IRQ_HANDLED;
}

/* A convenient way to quickly get R0 status.  The caller must _not_ hold the
 * port lock, it is acquired here.
 */
static __inline__ unsigned char ip22zilog_read_channel_status(struct uart_port *port)
{
      struct zilog_channel *channel;
      unsigned char status;

      channel = ZILOG_CHANNEL_FROM_PORT(port);
      status = readb(&channel->control);
      ZSDELAY();

      return status;
}

/* The port lock is not held.  */
static unsigned int ip22zilog_tx_empty(struct uart_port *port)
{
      unsigned long flags;
      unsigned char status;
      unsigned int ret;

      spin_lock_irqsave(&port->lock, flags);

      status = ip22zilog_read_channel_status(port);

      spin_unlock_irqrestore(&port->lock, flags);

      if (status & Tx_BUF_EMP)
            ret = TIOCSER_TEMT;
      else
            ret = 0;

      return ret;
}

/* The port lock is held and interrupts are disabled.  */
static unsigned int ip22zilog_get_mctrl(struct uart_port *port)
{
      unsigned char status;
      unsigned int ret;

      status = ip22zilog_read_channel_status(port);

      ret = 0;
      if (status & DCD)
            ret |= TIOCM_CAR;
      if (status & SYNC)
            ret |= TIOCM_DSR;
      if (status & CTS)
            ret |= TIOCM_CTS;

      return ret;
}

/* The port lock is held and interrupts are disabled.  */
static void ip22zilog_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;
      struct zilog_channel *channel = ZILOG_CHANNEL_FROM_PORT(port);
      unsigned char set_bits, clear_bits;

      set_bits = clear_bits = 0;

      if (mctrl & TIOCM_RTS)
            set_bits |= RTS;
      else
            clear_bits |= RTS;
      if (mctrl & TIOCM_DTR)
            set_bits |= DTR;
      else
            clear_bits |= DTR;

      /* NOTE: Not subject to 'transmitter active' rule.  */
      up->curregs[R5] |= set_bits;
      up->curregs[R5] &= ~clear_bits;
      write_zsreg(channel, R5, up->curregs[R5]);
}

/* The port lock is held and interrupts are disabled.  */
static void ip22zilog_stop_tx(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;

      up->flags |= IP22ZILOG_FLAG_TX_STOPPED;
}

/* The port lock is held and interrupts are disabled.  */
static void ip22zilog_start_tx(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;
      struct zilog_channel *channel = ZILOG_CHANNEL_FROM_PORT(port);
      unsigned char status;

      up->flags |= IP22ZILOG_FLAG_TX_ACTIVE;
      up->flags &= ~IP22ZILOG_FLAG_TX_STOPPED;

      status = readb(&channel->control);
      ZSDELAY();

      /* TX busy?  Just wait for the TX done interrupt.  */
      if (!(status & Tx_BUF_EMP))
            return;

      /* Send the first character to jump-start the TX done
       * IRQ sending engine.
       */
      if (port->x_char) {
            writeb(port->x_char, &channel->data);
            ZSDELAY();
            ZS_WSYNC(channel);

            port->icount.tx++;
            port->x_char = 0;
      } else {
            struct circ_buf *xmit = &port->info->xmit;

            writeb(xmit->buf[xmit->tail], &channel->data);
            ZSDELAY();
            ZS_WSYNC(channel);

            xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
            port->icount.tx++;

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

/* The port lock is held and interrupts are disabled.  */
static void ip22zilog_stop_rx(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = UART_ZILOG(port);
      struct zilog_channel *channel;

      if (ZS_IS_CONS(up))
            return;

      channel = ZILOG_CHANNEL_FROM_PORT(port);

      /* Disable all RX interrupts.  */
      up->curregs[R1] &= ~RxINT_MASK;
      ip22zilog_maybe_update_regs(up, channel);
}

/* The port lock is held.  */
static void ip22zilog_enable_ms(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;
      struct zilog_channel *channel = ZILOG_CHANNEL_FROM_PORT(port);
      unsigned char new_reg;

      new_reg = up->curregs[R15] | (DCDIE | SYNCIE | CTSIE);
      if (new_reg != up->curregs[R15]) {
            up->curregs[R15] = new_reg;

            /* NOTE: Not subject to 'transmitter active' rule.  */
            write_zsreg(channel, R15, up->curregs[R15]);
      }
}

/* The port lock is not held.  */
static void ip22zilog_break_ctl(struct uart_port *port, int break_state)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;
      struct zilog_channel *channel = ZILOG_CHANNEL_FROM_PORT(port);
      unsigned char set_bits, clear_bits, new_reg;
      unsigned long flags;

      set_bits = clear_bits = 0;

      if (break_state)
            set_bits |= SND_BRK;
      else
            clear_bits |= SND_BRK;

      spin_lock_irqsave(&port->lock, flags);

      new_reg = (up->curregs[R5] | set_bits) & ~clear_bits;
      if (new_reg != up->curregs[R5]) {
            up->curregs[R5] = new_reg;

            /* NOTE: Not subject to 'transmitter active' rule.  */
            write_zsreg(channel, R5, up->curregs[R5]);
      }

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

static void __ip22zilog_reset(struct uart_ip22zilog_port *up)
{
      struct zilog_channel *channel;
      int i;

      if (up->flags & IP22ZILOG_FLAG_RESET_DONE)
            return;

      /* Let pending transmits finish.  */
      channel = ZILOG_CHANNEL_FROM_PORT(&up->port);
      for (i = 0; i < 1000; i++) {
            unsigned char stat = read_zsreg(channel, R1);
            if (stat & ALL_SNT)
                  break;
            udelay(100);
      }

      if (!ZS_IS_CHANNEL_A(up)) {
            up++;
            channel = ZILOG_CHANNEL_FROM_PORT(&up->port);
      }
      write_zsreg(channel, R9, FHWRES);
      ZSDELAY_LONG();
      (void) read_zsreg(channel, R0);

      up->flags |= IP22ZILOG_FLAG_RESET_DONE;
      up->next->flags |= IP22ZILOG_FLAG_RESET_DONE;
}

static void __ip22zilog_startup(struct uart_ip22zilog_port *up)
{
      struct zilog_channel *channel;

      channel = ZILOG_CHANNEL_FROM_PORT(&up->port);

      __ip22zilog_reset(up);

      __load_zsregs(channel, up->curregs);
      /* set master interrupt enable */
      write_zsreg(channel, R9, up->curregs[R9]);
      up->prev_status = readb(&channel->control);

      /* Enable receiver and transmitter.  */
      up->curregs[R3] |= RxENAB;
      up->curregs[R5] |= TxENAB;

      up->curregs[R1] |= EXT_INT_ENAB | INT_ALL_Rx | TxINT_ENAB;
      ip22zilog_maybe_update_regs(up, channel);
}

static int ip22zilog_startup(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = UART_ZILOG(port);
      unsigned long flags;

      if (ZS_IS_CONS(up))
            return 0;

      spin_lock_irqsave(&port->lock, flags);
      __ip22zilog_startup(up);
      spin_unlock_irqrestore(&port->lock, flags);
      return 0;
}

/*
 * The test for ZS_IS_CONS is explained by the following e-mail:
 *****
 * From: Russell King <rmk@arm.linux.org.uk>
 * Date: Sun, 8 Dec 2002 10:18:38 +0000
 *
 * On Sun, Dec 08, 2002 at 02:43:36AM -0500, Pete Zaitcev wrote:
 * > I boot my 2.5 boxes using "console=ttyS0,9600" argument,
 * > and I noticed that something is not right with reference
 * > counting in this case. It seems that when the console
 * > is open by kernel initially, this is not accounted
 * > as an open, and uart_startup is not called.
 *
 * That is correct.  We are unable to call uart_startup when the serial
 * console is initialised because it may need to allocate memory (as
 * request_irq does) and the memory allocators may not have been
 * initialised.
 *
 * 1. initialise the port into a state where it can send characters in the
 *    console write method.
 *
 * 2. don't do the actual hardware shutdown in your shutdown() method (but
 *    do the normal software shutdown - ie, free irqs etc)
 *****
 */
static void ip22zilog_shutdown(struct uart_port *port)
{
      struct uart_ip22zilog_port *up = UART_ZILOG(port);
      struct zilog_channel *channel;
      unsigned long flags;

      if (ZS_IS_CONS(up))
            return;

      spin_lock_irqsave(&port->lock, flags);

      channel = ZILOG_CHANNEL_FROM_PORT(port);

      /* Disable receiver and transmitter.  */
      up->curregs[R3] &= ~RxENAB;
      up->curregs[R5] &= ~TxENAB;

      /* Disable all interrupts and BRK assertion.  */
      up->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
      up->curregs[R5] &= ~SND_BRK;
      ip22zilog_maybe_update_regs(up, channel);

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

/* Shared by TTY driver and serial console setup.  The port lock is held
 * and local interrupts are disabled.
 */
static void
ip22zilog_convert_to_zs(struct uart_ip22zilog_port *up, unsigned int cflag,
                   unsigned int iflag, int brg)
{

      up->curregs[R10] = NRZ;
      up->curregs[R11] = TCBR | RCBR;

      /* Program BAUD and clock source. */
      up->curregs[R4] &= ~XCLK_MASK;
      up->curregs[R4] |= X16CLK;
      up->curregs[R12] = brg & 0xff;
      up->curregs[R13] = (brg >> 8) & 0xff;
      up->curregs[R14] = BRENAB;

      /* Character size, stop bits, and parity. */
      up->curregs[3] &= ~RxN_MASK;
      up->curregs[5] &= ~TxN_MASK;
      switch (cflag & CSIZE) {
      case CS5:
            up->curregs[3] |= Rx5;
            up->curregs[5] |= Tx5;
            up->parity_mask = 0x1f;
            break;
      case CS6:
            up->curregs[3] |= Rx6;
            up->curregs[5] |= Tx6;
            up->parity_mask = 0x3f;
            break;
      case CS7:
            up->curregs[3] |= Rx7;
            up->curregs[5] |= Tx7;
            up->parity_mask = 0x7f;
            break;
      case CS8:
      default:
            up->curregs[3] |= Rx8;
            up->curregs[5] |= Tx8;
            up->parity_mask = 0xff;
            break;
      };
      up->curregs[4] &= ~0x0c;
      if (cflag & CSTOPB)
            up->curregs[4] |= SB2;
      else
            up->curregs[4] |= SB1;
      if (cflag & PARENB)
            up->curregs[4] |= PAR_ENAB;
      else
            up->curregs[4] &= ~PAR_ENAB;
      if (!(cflag & PARODD))
            up->curregs[4] |= PAR_EVEN;
      else
            up->curregs[4] &= ~PAR_EVEN;

      up->port.read_status_mask = Rx_OVR;
      if (iflag & INPCK)
            up->port.read_status_mask |= CRC_ERR | PAR_ERR;
      if (iflag & (BRKINT | PARMRK))
            up->port.read_status_mask |= BRK_ABRT;

      up->port.ignore_status_mask = 0;
      if (iflag & IGNPAR)
            up->port.ignore_status_mask |= CRC_ERR | PAR_ERR;
      if (iflag & IGNBRK) {
            up->port.ignore_status_mask |= BRK_ABRT;
            if (iflag & IGNPAR)
                  up->port.ignore_status_mask |= Rx_OVR;
      }

      if ((cflag & CREAD) == 0)
            up->port.ignore_status_mask = 0xff;
}

/* The port lock is not held.  */
static void
ip22zilog_set_termios(struct uart_port *port, struct ktermios *termios,
                  struct ktermios *old)
{
      struct uart_ip22zilog_port *up = (struct uart_ip22zilog_port *) port;
      unsigned long flags;
      int baud, brg;

      baud = uart_get_baud_rate(port, termios, old, 1200, 76800);

      spin_lock_irqsave(&up->port.lock, flags);

      brg = BPS_TO_BRG(baud, ZS_CLOCK / ZS_CLOCK_DIVISOR);

      ip22zilog_convert_to_zs(up, termios->c_cflag, termios->c_iflag, brg);

      if (UART_ENABLE_MS(&up->port, termios->c_cflag))
            up->flags |= IP22ZILOG_FLAG_MODEM_STATUS;
      else
            up->flags &= ~IP22ZILOG_FLAG_MODEM_STATUS;

      ip22zilog_maybe_update_regs(up, ZILOG_CHANNEL_FROM_PORT(port));
      uart_update_timeout(port, termios->c_cflag, baud);

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

static const char *ip22zilog_type(struct uart_port *port)
{
      return "IP22-Zilog";
}

/* We do not request/release mappings of the registers here, this
 * happens at early serial probe time.
 */
static void ip22zilog_release_port(struct uart_port *port)
{
}

static int ip22zilog_request_port(struct uart_port *port)
{
      return 0;
}

/* These do not need to do anything interesting either.  */
static void ip22zilog_config_port(struct uart_port *port, int flags)
{
}

/* We do not support letting the user mess with the divisor, IRQ, etc. */
static int ip22zilog_verify_port(struct uart_port *port, struct serial_struct *ser)
{
      return -EINVAL;
}

static struct uart_ops ip22zilog_pops = {
      .tx_empty   =     ip22zilog_tx_empty,
      .set_mctrl  =     ip22zilog_set_mctrl,
      .get_mctrl  =     ip22zilog_get_mctrl,
      .stop_tx    =     ip22zilog_stop_tx,
      .start_tx   =     ip22zilog_start_tx,
      .stop_rx    =     ip22zilog_stop_rx,
      .enable_ms  =     ip22zilog_enable_ms,
      .break_ctl  =     ip22zilog_break_ctl,
      .startup    =     ip22zilog_startup,
      .shutdown   =     ip22zilog_shutdown,
      .set_termios      =     ip22zilog_set_termios,
      .type       =     ip22zilog_type,
      .release_port     =     ip22zilog_release_port,
      .request_port     =     ip22zilog_request_port,
      .config_port      =     ip22zilog_config_port,
      .verify_port      =     ip22zilog_verify_port,
};

static struct uart_ip22zilog_port *ip22zilog_port_table;
static struct zilog_layout **ip22zilog_chip_regs;

static struct uart_ip22zilog_port *ip22zilog_irq_chain;
static int zilog_irq = -1;

static void * __init alloc_one_table(unsigned long size)
{
      return kzalloc(size, GFP_KERNEL);
}

static void __init ip22zilog_alloc_tables(void)
{
      ip22zilog_port_table = (struct uart_ip22zilog_port *)
            alloc_one_table(NUM_CHANNELS * sizeof(struct uart_ip22zilog_port));
      ip22zilog_chip_regs = (struct zilog_layout **)
            alloc_one_table(NUM_IP22ZILOG * sizeof(struct zilog_layout *));

      if (ip22zilog_port_table == NULL || ip22zilog_chip_regs == NULL) {
            panic("IP22-Zilog: Cannot allocate IP22-Zilog tables.");
      }
}

/* Get the address of the registers for IP22-Zilog instance CHIP.  */
static struct zilog_layout * __init get_zs(int chip)
{
      unsigned long base;

      if (chip < 0 || chip >= NUM_IP22ZILOG) {
            panic("IP22-Zilog: Illegal chip number %d in get_zs.", chip);
      }

      /* Not probe-able, hard code it. */
      base = (unsigned long) &sgioc->uart;

      zilog_irq = SGI_SERIAL_IRQ;
      request_mem_region(base, 8, "IP22-Zilog");

      return (struct zilog_layout *) base;
}

#define ZS_PUT_CHAR_MAX_DELAY 2000  /* 10 ms */

#ifdef CONFIG_SERIAL_IP22_ZILOG_CONSOLE
static void ip22zilog_put_char(struct uart_port *port, int ch)
{
      struct zilog_channel *channel = ZILOG_CHANNEL_FROM_PORT(port);
      int loops = ZS_PUT_CHAR_MAX_DELAY;

      /* This is a timed polling loop so do not switch the explicit
       * udelay with ZSDELAY as that is a NOP on some platforms.  -DaveM
       */
      do {
            unsigned char val = readb(&channel->control);
            if (val & Tx_BUF_EMP) {
                  ZSDELAY();
                  break;
            }
            udelay(5);
      } while (--loops);

      writeb(ch, &channel->data);
      ZSDELAY();
      ZS_WSYNC(channel);
}

static void
ip22zilog_console_write(struct console *con, const char *s, unsigned int count)
{
      struct uart_ip22zilog_port *up = &ip22zilog_port_table[con->index];
      unsigned long flags;

      spin_lock_irqsave(&up->port.lock, flags);
      uart_console_write(&up->port, s, count, ip22zilog_put_char);
      udelay(2);
      spin_unlock_irqrestore(&up->port.lock, flags);
}

static int __init ip22zilog_console_setup(struct console *con, char *options)
{
      struct uart_ip22zilog_port *up = &ip22zilog_port_table[con->index];
      unsigned long flags;
      int baud = 9600, bits = 8;
      int parity = 'n';
      int flow = 'n';

      up->flags |= IP22ZILOG_FLAG_IS_CONS;

      printk(KERN_INFO "Console: ttyS%d (IP22-Zilog)\n", con->index);

      spin_lock_irqsave(&up->port.lock, flags);

      up->curregs[R15] |= BRKIE;

      __ip22zilog_startup(up);

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

      if (options)
            uart_parse_options(options, &baud, &parity, &bits, &flow);
      return uart_set_options(&up->port, con, baud, parity, bits, flow);
}

static struct uart_driver ip22zilog_reg;

static struct console ip22zilog_console = {
      .name =     "ttyS",
      .write      =     ip22zilog_console_write,
      .device     =     uart_console_device,
      .setup      =     ip22zilog_console_setup,
      .flags      =     CON_PRINTBUFFER,
      .index      =     -1,
      .data =     &ip22zilog_reg,
};
#endif /* CONFIG_SERIAL_IP22_ZILOG_CONSOLE */

static struct uart_driver ip22zilog_reg = {
      .owner            = THIS_MODULE,
      .driver_name      = "serial",
      .dev_name   = "ttyS",
      .major            = TTY_MAJOR,
      .minor            = 64,
      .nr         = NUM_CHANNELS,
#ifdef CONFIG_SERIAL_IP22_ZILOG_CONSOLE
      .cons       = &ip22zilog_console,
#endif
};

static void __init ip22zilog_prepare(void)
{
      struct uart_ip22zilog_port *up;
      struct zilog_layout *rp;
      int channel, chip;

      /*
       * Temporary fix.
       */
      for (channel = 0; channel < NUM_CHANNELS; channel++)
            spin_lock_init(&ip22zilog_port_table[channel].port.lock);

      ip22zilog_irq_chain = &ip22zilog_port_table[NUM_CHANNELS - 1];
        up = &ip22zilog_port_table[0];
      for (channel = NUM_CHANNELS - 1 ; channel > 0; channel--)
            up[channel].next = &up[channel - 1];
      up[channel].next = NULL;

      for (chip = 0; chip < NUM_IP22ZILOG; chip++) {
            if (!ip22zilog_chip_regs[chip]) {
                  ip22zilog_chip_regs[chip] = rp = get_zs(chip);

                  up[(chip * 2) + 0].port.membase = (char *) &rp->channelB;
                  up[(chip * 2) + 1].port.membase = (char *) &rp->channelA;

                  /* In theory mapbase is the physical address ...  */
                  up[(chip * 2) + 0].port.mapbase =
                        (unsigned long) ioremap((unsigned long) &rp->channelB, 8);
                  up[(chip * 2) + 1].port.mapbase =
                        (unsigned long) ioremap((unsigned long) &rp->channelA, 8);
            }

            /* Channel A */
            up[(chip * 2) + 0].port.iotype = UPIO_MEM;
            up[(chip * 2) + 0].port.irq = zilog_irq;
            up[(chip * 2) + 0].port.uartclk = ZS_CLOCK;
            up[(chip * 2) + 0].port.fifosize = 1;
            up[(chip * 2) + 0].port.ops = &ip22zilog_pops;
            up[(chip * 2) + 0].port.type = PORT_IP22ZILOG;
            up[(chip * 2) + 0].port.flags = 0;
            up[(chip * 2) + 0].port.line = (chip * 2) + 0;
            up[(chip * 2) + 0].flags = 0;

            /* Channel B */
            up[(chip * 2) + 1].port.iotype = UPIO_MEM;
            up[(chip * 2) + 1].port.irq = zilog_irq;
            up[(chip * 2) + 1].port.uartclk = ZS_CLOCK;
            up[(chip * 2) + 1].port.fifosize = 1;
            up[(chip * 2) + 1].port.ops = &ip22zilog_pops;
            up[(chip * 2) + 1].port.type = PORT_IP22ZILOG;
            up[(chip * 2) + 1].port.line = (chip * 2) + 1;
            up[(chip * 2) + 1].flags |= IP22ZILOG_FLAG_IS_CHANNEL_A;
      }

      for (channel = 0; channel < NUM_CHANNELS; channel++) {
            struct uart_ip22zilog_port *up = &ip22zilog_port_table[channel];
            int brg;

            /* Normal serial TTY. */
            up->parity_mask = 0xff;
            up->curregs[R1] = EXT_INT_ENAB | INT_ALL_Rx | TxINT_ENAB;
            up->curregs[R4] = PAR_EVEN | X16CLK | SB1;
            up->curregs[R3] = RxENAB | Rx8;
            up->curregs[R5] = TxENAB | Tx8;
            up->curregs[R9] = NV | MIE;
            up->curregs[R10] = NRZ;
            up->curregs[R11] = TCBR | RCBR;
            brg = BPS_TO_BRG(9600, ZS_CLOCK / ZS_CLOCK_DIVISOR);
            up->curregs[R12] = (brg & 0xff);
            up->curregs[R13] = (brg >> 8) & 0xff;
            up->curregs[R14] = BRENAB;
      }
}

static int __init ip22zilog_ports_init(void)
{
      int ret;

      printk(KERN_INFO "Serial: IP22 Zilog driver (%d chips).\n", NUM_IP22ZILOG);

      ip22zilog_prepare();

      if (request_irq(zilog_irq, ip22zilog_interrupt, 0,
                  "IP22-Zilog", ip22zilog_irq_chain)) {
            panic("IP22-Zilog: Unable to register zs interrupt handler.\n");
      }

      ret = uart_register_driver(&ip22zilog_reg);
      if (ret == 0) {
            int i;

            for (i = 0; i < NUM_CHANNELS; i++) {
                  struct uart_ip22zilog_port *up = &ip22zilog_port_table[i];

                  uart_add_one_port(&ip22zilog_reg, &up->port);
            }
      }

      return ret;
}

static int __init ip22zilog_init(void)
{
      /* IP22 Zilog setup is hard coded, no probing to do.  */
      ip22zilog_alloc_tables();
      ip22zilog_ports_init();

      return 0;
}

static void __exit ip22zilog_exit(void)
{
      int i;
      struct uart_ip22zilog_port *up;

      for (i = 0; i < NUM_CHANNELS; i++) {
            up = &ip22zilog_port_table[i];

            uart_remove_one_port(&ip22zilog_reg, &up->port);
      }

      /* Free IO mem */
      up = &ip22zilog_port_table[0];
      for (i = 0; i < NUM_IP22ZILOG; i++) {
            if (up[(i * 2) + 0].port.mapbase) {
               iounmap((void*)up[(i * 2) + 0].port.mapbase);
               up[(i * 2) + 0].port.mapbase = 0;
            }
            if (up[(i * 2) + 1].port.mapbase) {
                  iounmap((void*)up[(i * 2) + 1].port.mapbase);
                  up[(i * 2) + 1].port.mapbase = 0;
            }
      }

      uart_unregister_driver(&ip22zilog_reg);
}

module_init(ip22zilog_init);
module_exit(ip22zilog_exit);

/* David wrote it but I'm to blame for the bugs ...  */
MODULE_AUTHOR("Ralf Baechle <ralf@linux-mips.org>");
MODULE_DESCRIPTION("SGI Zilog serial port driver");
MODULE_LICENSE("GPL");

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