Subversion Repositories openrisc_2011-10-31

//==========================================================================

//

//      tx3904_serial.c

//

//      Serial device driver for TX3904 on-chip serial devices

//

//==========================================================================

//####ECOSGPLCOPYRIGHTBEGIN####

// -------------------------------------------

// This file is part of eCos, the Embedded Configurable Operating System.

// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

//

// eCos is free software; you can redistribute it and/or modify it under

// the terms of the GNU General Public License as published by the Free

// Software Foundation; either version 2 or (at your option) any later version.

//

// eCos is distributed in the hope that it will be useful, but WITHOUT ANY

// WARRANTY; without even the implied warranty of MERCHANTABILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with eCos; if not, write to the Free Software Foundation, Inc.,

// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.

//

// As a special exception, if other files instantiate templates or use macros

// or inline functions from this file, or you compile this file and link it

// with other works to produce a work based on this file, this file does not

// by itself cause the resulting work to be covered by the GNU General Public

// License. However the source code for this file must still be made available

// in accordance with section (3) of the GNU General Public License.

//

// This exception does not invalidate any other reasons why a work based on

// this file might be covered by the GNU General Public License.

//

// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.

// at http://sources.redhat.com/ecos/ecos-license/

// -------------------------------------------

//####ECOSGPLCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):   nickg

// Contributors: nickg

// Date:        1999-03-3

// Purpose:     TX3904 serial device driver

// Description: TX3904 serial device driver

//

//####DESCRIPTIONEND####

//

//==========================================================================

#include <pkgconf/hal.h>

#include <pkgconf/io_serial.h>

#include <cyg/hal/hal_io.h>

#include <cyg/hal/hal_intr.h>

#include <cyg/io/io.h>

#include <cyg/io/devtab.h>

#include <cyg/io/serial.h>

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904

cyg_bool cyg_hal_is_break(char *buf, int size);

void cyg_hal_user_break( CYG_ADDRWORD *regs );

//-------------------------------------------------------------------------

extern void diag_printf(const char *fmt, ...);

//-------------------------------------------------------------------------

// Forward definitions

static bool tx3904_serial_init(struct cyg_devtab_entry *tab);

static bool tx3904_serial_putc(serial_channel *chan, unsigned char c);

static Cyg_ErrNo tx3904_serial_lookup(struct cyg_devtab_entry **tab,

                                   struct cyg_devtab_entry *sub_tab,

                                   const char *name);

static unsigned char tx3904_serial_getc(serial_channel *chan);

static Cyg_ErrNo tx3904_serial_set_config(serial_channel *chan, cyg_uint32 key,

                                          const void *xbuf, cyg_uint32 *len);

static void tx3904_serial_start_xmit(serial_channel *chan);

static void tx3904_serial_stop_xmit(serial_channel *chan);

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE

static cyg_uint32 tx3904_serial_ISR(cyg_vector_t vector, cyg_addrword_t data, cyg_addrword_t *regs);

static void       tx3904_serial_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data);

#endif

//-------------------------------------------------------------------------

// TX3904 serial line control register values:

// Offsets to serial control registers from base

#define SERIAL_CR       0x00

#define SERIAL_SR       0x04

#define SERIAL_ICR      0x08

#define SERIAL_ISR      0x0C

#define SERIAL_FCR      0x10

#define SERIAL_BRG      0x14

#define SERIAL_TXB      0x20

#define SERIAL_RXB      0x30

// Status register bits

#define ISR_RXRDY       0x01

#define ISR_TXRDY       0x02

#define ISR_ERROR       0x04

// Control register bits

#define LCR_SB1         0x0000

#define LCR_SB1_5       0x0000

#define LCR_SB2         0x0004

#define LCR_PN          0x0000    // Parity mode - none

#define LCR_PS          0x0000    // Forced "space" parity

#define LCR_PM          0x0000    // Forced "mark" parity

#define LCR_PE          0x0018    // Parity mode - even

#define LCR_PO          0x0010    // Parity mode - odd

#define LCR_WL5         0x0001    // not supported - use 7bit

#define LCR_WL6         0x0001    // not supported - use 7bit

#define LCR_WL7         0x0001    // 7 bit chars

#define LCR_WL8         0x0000    // 8 bit chars

#define LCR_BRG         0x0020    // Select baud rate generator

#define ICR_RXE         0x0001  // receive enable

#define ICR_TXE         0x0002  // transmit enable

//-------------------------------------------------------------------------

// Tables to map input values to hardware settings

static unsigned char select_word_length[] = {

    LCR_WL5,    // 5 bits / word (char)

    LCR_WL6,

    LCR_WL7,

    LCR_WL8

};

static unsigned char select_stop_bits[] = {

    0,

    LCR_SB1,    // 1 stop bit

    LCR_SB1_5,  // 1.5 stop bit

    LCR_SB2     // 2 stop bits

};

static unsigned char select_parity[] = {

    LCR_PN,     // No parity

    LCR_PE,     // Even parity

    LCR_PO,     // Odd parity

    LCR_PM,     // Mark parity

    LCR_PS,     // Space parity

};

// The values in this table plug straight into the BRG register

// in the serial driver hardware. They comprise a baud rate divisor

// in the bottom 8 bits and a clock selector in the top 8 bits.

// These figures all come from Toshiba.

#if (CYGHWR_HAL_MIPS_CPU_FREQ == 50)

static unsigned short select_baud[] = {

    0,          // Unused

    0,          // 50

    0,          // 75

    0,          // 110

    0,          // 134.5

    0,          // 150

    0,          // 200

    0,          // 300

    0x0300|20,  // 600

    0x0300|10,  // 1200

    0,          // 1800

    0x0300|05,  // 2400

    0,          // 3600

    0x0300|10,  // 4800

    0,          // 7200

    0x0200|05,  // 9600

    0,          // 14400

    0x0100|10,  // 19200

    0x0100|05,  // 38400

    0,          // 57600

    0,          // 115200

    0,          // 230400

};

#elif (CYGHWR_HAL_MIPS_CPU_FREQ == 66)

static unsigned short select_baud[] = {

    0,          // Unused

    0,          // 50

    0,          // 75

    0,          // 110

    0,          // 134.5

    0,          // 150

    0,          // 200

    0,          // 300

    0x0300|27,  // 600

    0x0200|54,  // 1200

    0,          // 1800

    0x0200|27,  // 2400

    0,          // 3600

    0x0100|54,  // 4800

    0,          // 7200

    0x0100|27,  // 9600

    0,          // 14400

    0x0000|54,  // 19200

    0x0000|27,  // 38400

    0,          // 57600

    0,          // 115200

    0,          // 230400

};

#else

#error Unsupported CPU frequency

#endif

//-------------------------------------------------------------------------

// Info for each serial device controlled

typedef struct tx3904_serial_info {

    CYG_ADDRWORD   base;

    CYG_WORD       int_num;

    cyg_interrupt  interrupt;

    cyg_handle_t   interrupt_handle;

    cyg_uint8      input_char;

    cyg_bool       input_char_valid;

    cyg_bool       output_ready;

    cyg_uint16     cur_baud;

} tx3904_serial_info;

//-------------------------------------------------------------------------

// Callback functions exported by this driver

static SERIAL_FUNS(tx3904_serial_funs,

                   tx3904_serial_putc,

                   tx3904_serial_getc,

                   tx3904_serial_set_config,

                   tx3904_serial_start_xmit,

                   tx3904_serial_stop_xmit

    );

//-------------------------------------------------------------------------

// Hardware info for each serial line

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

static tx3904_serial_info tx3904_serial_info0 = {

    0xFFFFF300,

    CYGNUM_HAL_INTERRUPT_SIO_0

};

#if CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BUFSIZE > 0

static unsigned char tx3904_serial_out_buf0[CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BUFSIZE];

static unsigned char tx3904_serial_in_buf0[CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BUFSIZE];

#endif

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

static tx3904_serial_info tx3904_serial_info1 = {

    0xFFFFF400,

    CYGNUM_HAL_INTERRUPT_SIO_1

};

#if CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BUFSIZE > 0

static unsigned char tx3904_serial_out_buf1[CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BUFSIZE];

static unsigned char tx3904_serial_in_buf1[CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BUFSIZE];

#endif

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

//-------------------------------------------------------------------------

// Channel descriptions:

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE

#define SIZEOF_BUF(_x_) 0

#else

#define SIZEOF_BUF(_x_) sizeof(_x_)

#endif

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

#if CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BUFSIZE > 0

static SERIAL_CHANNEL_USING_INTERRUPTS(tx3904_serial_channel0,

                                       tx3904_serial_funs,

                                       tx3904_serial_info0,

                                       CYG_SERIAL_BAUD_RATE(CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BAUD),

                                       CYG_SERIAL_STOP_DEFAULT,

                                       CYG_SERIAL_PARITY_DEFAULT,

                                       CYG_SERIAL_WORD_LENGTH_DEFAULT,

                                       CYG_SERIAL_FLAGS_DEFAULT,

                                       &tx3904_serial_out_buf0[0],

                                       SIZEOF_BUF(tx3904_serial_out_buf0),

                                       &tx3904_serial_in_buf0[0],

                                       SIZEOF_BUF(tx3904_serial_in_buf0)

    );

#else

static SERIAL_CHANNEL(tx3904_serial_channel0,

                      tx3904_serial_funs,

                      tx3904_serial_info0,

                      CYG_SERIAL_BAUD_RATE(CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL0_BAUD),

                      CYG_SERIAL_STOP_DEFAULT,

                      CYG_SERIAL_PARITY_DEFAULT,

                      CYG_SERIAL_WORD_LENGTH_DEFAULT,

                      CYG_SERIAL_FLAGS_DEFAULT

    );

#endif

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

#if CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BUFSIZE > 0

static SERIAL_CHANNEL_USING_INTERRUPTS(tx3904_serial_channel1,

                                       tx3904_serial_funs,

                                       tx3904_serial_info1,

                                       CYG_SERIAL_BAUD_RATE(CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BAUD),

                                       CYG_SERIAL_STOP_DEFAULT,

                                       CYG_SERIAL_PARITY_DEFAULT,

                                       CYG_SERIAL_WORD_LENGTH_DEFAULT,

                                       CYG_SERIAL_FLAGS_DEFAULT,

                                       &tx3904_serial_out_buf1[0],

                                       SIZEOF_BUF(tx3904_serial_out_buf1),

                                       &tx3904_serial_in_buf1[0],

                                       SIZEOF_BUF(tx3904_serial_in_buf1)

    );

#else

static SERIAL_CHANNEL(tx3904_serial_channel1,

                      tx3904_serial_funs,

                      tx3904_serial_info1,

                      CYG_SERIAL_BAUD_RATE(CYGNUM_IO_SERIAL_TX39_JMR3904_SERIAL1_BAUD),

                      CYG_SERIAL_STOP_DEFAULT,

                      CYG_SERIAL_PARITY_DEFAULT,

                      CYG_SERIAL_WORD_LENGTH_DEFAULT,

                      CYG_SERIAL_FLAGS_DEFAULT

    );

#endif

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

//-------------------------------------------------------------------------

// And finally, the device table entries:

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

DEVTAB_ENTRY(tx3904_serial_io0,

             CYGDAT_IO_SERIAL_TX39_JMR3904_SERIAL0_NAME,

             0,                     // Does not depend on a lower level interface

             &cyg_io_serial_devio,

             tx3904_serial_init,

             tx3904_serial_lookup,     // Serial driver may need initializing

             &tx3904_serial_channel0

    );

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

DEVTAB_ENTRY(tx3904_serial_io1,

             CYGDAT_IO_SERIAL_TX39_JMR3904_SERIAL1_NAME,

             0,                     // Does not depend on a lower level interface

             &cyg_io_serial_devio,

             tx3904_serial_init,

             tx3904_serial_lookup,     // Serial driver may need initializing

             &tx3904_serial_channel1

    );

#endif // CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL1

// ------------------------------------------------------------------------

// Delay for some number of character times. This is based on the baud

// rate currently set. We use the numbers that plug in to the BRG

// clock select and divider to control two loops. The innermost delay

// loop uses a count that is derived from dividing the CPU frequency

// by the BRG granularity (and we then add 1 to compensate for any

// rounding).  This gives the number of cycles that the innermost loop

// must consume.  For the sake of simplicity we assume that this loop

// will take 1 cycle per loop, which is roughly true in optimized

// code.

void delay_char_time(tx3904_serial_info *tx3904_chan, int n)

{

    static cyg_uint16 clock_val[4] = { 4, 16, 64, 256 };

    cyg_uint16 baud_val = select_baud[tx3904_chan->cur_baud];

    cyg_count32 clock_loop = clock_val[baud_val>>8];

    cyg_count32 div_loop = baud_val & 0xFF;

    cyg_count32 bit_time = ((CYGHWR_HAL_MIPS_CPU_FREQ_ACTUAL)/(2457600)) + 1;

    n *= 11;    // allow for start and stop bits and 8 data bits

    while( n-- )

    {

        cyg_count32 i,j,k;

        for( i = 0; i < clock_loop; i++ )

            for( j = 0; j < div_loop; j++ )

                for( k = 0; k < bit_time; k++ )

                    continue;

    }

}

//-------------------------------------------------------------------------

static bool

tx3904_serial_config_port(serial_channel *chan, cyg_serial_info_t *new_config, bool init)

{

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint16 cr = 0;

    cyg_uint16 icr = 0;

    cyg_uint16 baud_divisor = select_baud[new_config->baud];

    if (baud_divisor == 0)

        return false;  // Invalid baud rate selected

    // set up other config values:

    cr |= select_word_length[new_config->word_length - CYGNUM_SERIAL_WORD_LENGTH_5];

    cr |= select_stop_bits[new_config->stop];

    cr |= select_parity[new_config->parity];

    // Source transfer clock from BRG

    cr |= LCR_BRG;

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE    

    // Enable RX interrupts only at present

#ifdef CYGPKG_IO_SERIAL_TX39_JMR3904_SERIAL0

    if ((chan->out_cbuf.len != 0) || (chan == &tx3904_serial_channel0)) {

#else

    if (chan->out_cbuf.len != 0) {

#endif

        icr |= ICR_RXE;

    }

#endif

    // Avoid any interrupts while we are fiddling with the line parameters.

    cyg_drv_interrupt_mask(tx3904_chan->int_num);

    // In theory we should wait here for the transmitter to drain the

    // FIFO so we dont change the line parameters with characters

    // unsent. Unfortunately the TX39 serial devices do not allow us

    // to discover when the FIFO is empty.

    delay_char_time(tx3904_chan, 8);

    // Disable device entirely.

//    HAL_WRITE_UINT16(tx3904_chan->base+SERIAL_CR, 0);

//    HAL_WRITE_UINT8(tx3904_chan->base+SERIAL_ICR, 0);

    // Reset the FIFOs

    HAL_WRITE_UINT16(tx3904_chan->base+SERIAL_FCR, 7);

    HAL_WRITE_UINT16(tx3904_chan->base+SERIAL_FCR, 0);

    // Set up baud rate

    HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_BRG, baud_divisor );

    // Write CR into hardware

    HAL_WRITE_UINT16(tx3904_chan->base+SERIAL_CR, cr);

    // Write ICR into hardware

    HAL_WRITE_UINT16(tx3904_chan->base+SERIAL_ICR, icr);

    // Re-enable interrupts.

    cyg_drv_interrupt_unmask(tx3904_chan->int_num);

    // Save current baud rate

    tx3904_chan->cur_baud = new_config->baud;

    if (new_config != &chan->config) {

        chan->config = *new_config;

    }

    return true;

}

//-------------------------------------------------------------------------

// Function to initialize the device.  Called at bootstrap time.

bool tx3904_serial_init(struct cyg_devtab_entry *tab)

{

    serial_channel *chan = (serial_channel *)tab->priv;

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    (chan->callbacks->serial_init)(chan);  // Really only required for interrupt driven devices

    tx3904_chan->cur_baud = CYGNUM_SERIAL_BAUD_38400;

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE    

    if (chan->out_cbuf.len != 0) {

        // Install and enable the interrupt

        cyg_drv_interrupt_create(tx3904_chan->int_num,

                                 4,                      // Priority

                                 (cyg_addrword_t)chan,   //  Data item passed to interrupt handler

                                 (cyg_ISR_t *)tx3904_serial_ISR,

                                 tx3904_serial_DSR,

                                 &tx3904_chan->interrupt_handle,

                                 &tx3904_chan->interrupt);

        cyg_drv_interrupt_attach(tx3904_chan->interrupt_handle);

        cyg_drv_interrupt_unmask(tx3904_chan->int_num);

    }

#endif

    tx3904_serial_config_port(chan, &chan->config, true);

    return true;

}

//-------------------------------------------------------------------------

// This routine is called when the device is "looked" up (i.e. attached)

static Cyg_ErrNo

tx3904_serial_lookup(struct cyg_devtab_entry **tab,

                  struct cyg_devtab_entry *sub_tab,

                  const char *name)

{

    serial_channel *chan = (serial_channel *)(*tab)->priv;

    (chan->callbacks->serial_init)(chan);  // Really only required for interrupt driven devices

    return ENOERR;

}

//-------------------------------------------------------------------------

// Return 'true' if character is sent to device

bool

tx3904_serial_putc(serial_channel *chan, unsigned char c)

{

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint16 isr;

    HAL_READ_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

    if( isr & ISR_TXRDY )

    {

        HAL_WRITE_UINT8( tx3904_chan->base+SERIAL_TXB, c );

        isr &= ~ISR_TXRDY;

        HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

        return true;

    }

    else return false;

}

//-------------------------------------------------------------------------

unsigned char

tx3904_serial_getc(serial_channel *chan)

{

    unsigned char c;

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint16 isr;

    do

    {

        HAL_READ_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

        // Eliminate any RX errors

        if( isr & ISR_ERROR )

        {

            cyg_uint16 sr = 0;

            isr &= ISR_ERROR;

//            HAL_READ_UINT16( tx3904_chan->base+SERIAL_SR, sr );

            HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_SR, sr );

            HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

        }

    } while( (isr & ISR_RXRDY) != ISR_RXRDY );

    HAL_READ_UINT8( tx3904_chan->base+SERIAL_RXB, c );

    isr &= ~ISR_RXRDY;

    HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

    return c;

}

//-------------------------------------------------------------------------

static Cyg_ErrNo

tx3904_serial_set_config(serial_channel *chan, cyg_uint32 key,

                         const void *xbuf, cyg_uint32 *len)

{

    switch (key) {

    case CYG_IO_SET_CONFIG_SERIAL_INFO:

      {

        cyg_serial_info_t *config = (cyg_serial_info_t *)xbuf;

        if ( *len < sizeof(cyg_serial_info_t) ) {

            return -EINVAL;

        }

        *len = sizeof(cyg_serial_info_t);

        if ( true != tx3904_serial_config_port(chan, config, false) )

            return -EINVAL;

      }

      break;

    default:

        return -EINVAL;

    }

    return ENOERR;

}

//-------------------------------------------------------------------------

// Enable the transmitter on the device

static void

tx3904_serial_start_xmit(serial_channel *chan)

{

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE    

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint16 icr;

    HAL_READ_UINT16( tx3904_chan->base+SERIAL_ICR, icr );

    icr |= ICR_TXE;

    HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ICR, icr );

#endif    

}

//-------------------------------------------------------------------------

// Disable the transmitter on the device

static void

tx3904_serial_stop_xmit(serial_channel *chan)

{

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE    

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint16 icr;

    HAL_READ_UINT16( tx3904_chan->base+SERIAL_ICR, icr );

    icr &= ~ICR_TXE;

    HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ICR, icr );

#endif    

}

//-------------------------------------------------------------------------

// Serial I/O - low level interrupt handlers (ISR)

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE

static cyg_uint32

tx3904_serial_ISR(cyg_vector_t vector, cyg_addrword_t data, cyg_addrword_t *regs)

{

    serial_channel *chan = (serial_channel *)data;

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint8 isr;

    cyg_uint32 result = 0;

    cyg_drv_interrupt_mask(tx3904_chan->int_num);

    cyg_drv_interrupt_acknowledge(tx3904_chan->int_num);

    HAL_READ_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

    // Eliminate any RX errors

    if( isr & ISR_ERROR )

    {

        cyg_uint16 sr = 0;

        isr &= ~ISR_ERROR;

        HAL_READ_UINT16( tx3904_chan->base+SERIAL_SR, sr );

        HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_SR, 0 );

    }

    // Check for a TX interrupt and set the flag if so.

    if( isr & ISR_TXRDY )

    {

        isr &= ~ISR_TXRDY;

        tx3904_chan->output_ready = true;

        result |= CYG_ISR_CALL_DSR;  // Cause DSR to be run

    }

    // Check here for an RX interrupt and fetch the character. If it

    // is a ^C then call into GDB stub to handle it.

    if( isr & ISR_RXRDY )

    {

        cyg_uint8 rxb;

        HAL_READ_UINT8( tx3904_chan->base+SERIAL_RXB, rxb );

        isr &= ~ISR_RXRDY;

        if( cyg_hal_is_break( &rxb , 1 ) )

            cyg_hal_user_break( regs );

        else

        {

            tx3904_chan->input_char = rxb;

            tx3904_chan->input_char_valid = true;

            result |= CYG_ISR_CALL_DSR;  // Cause DSR to be run

        }

    }

    HAL_WRITE_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

    return result;

}

#endif

//-------------------------------------------------------------------------

// Serial I/O - high level interrupt handler (DSR)

#ifndef CYGPKG_IO_SERIAL_TX39_JMR3904_POLLED_MODE

static void

tx3904_serial_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)

{

    serial_channel *chan = (serial_channel *)data;

    tx3904_serial_info *tx3904_chan = (tx3904_serial_info *)chan->dev_priv;

    cyg_uint8 isr;

    HAL_READ_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

    if( tx3904_chan->input_char_valid )

    {

        (chan->callbacks->rcv_char)(chan, tx3904_chan->input_char);

        tx3904_chan->input_char_valid = false;

#if 0        

        // And while we are here, pull any further characters out of the

        // FIFO. This should help to reduce the interrupt rate.

        HAL_READ_UINT16( tx3904_chan->base+SERIAL_ISR, isr );

        while( isr & ISR_RXRDY )