mipsidt_serial.c

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    // Disable port interrupts while changing hardware
    HAL_READ_UINT8(port+SER_16550_IER, _ier);
    HAL_WRITE_UINT8(port+SER_16550_IER, 0);

    // Set databits, stopbits and parity.
    _lcr = select_word_length[(new_config->word_length -
                               CYGNUM_SERIAL_WORD_LENGTH_5)] | 
        select_stop_bits[new_config->stop] |
        select_parity[new_config->parity];
    HAL_WRITE_UINT8(port+SER_16550_LCR, _lcr);

    // Set baud rate.
    _lcr |= LCR_DL;
    HAL_WRITE_UINT8(port+SER_16550_LCR, _lcr);
    HAL_WRITE_UINT8(port+SER_16550_DLM, baud_divisor >> 8);
    HAL_WRITE_UINT8(port+SER_16550_DLL, baud_divisor & 0xff);
    _lcr &= ~LCR_DL;
    HAL_WRITE_UINT8(port+SER_16550_LCR, _lcr);

    if (init) {
        // Enable and clear FIFO
        HAL_WRITE_UINT8(port+SER_16550_FCR,
                        (FCR_ENABLE | FCR_CLEAR_RCVR | FCR_CLEAR_XMIT));

        if (chan->out_cbuf.len != 0) {
            HAL_WRITE_UINT8(port+SER_16550_IER, SIO_IER_ERDAI);
        } else {
            HAL_WRITE_UINT8(port+SER_16550_IER, 0);
        }
    } else {
        HAL_WRITE_UINT8(port+SER_16550_IER, _ier);
    }
    if (new_config != &chan->config) {
        chan->config = *new_config;
    }
    return true;
}

// Function to initialize the device.  Called at bootstrap time.
static bool 
mipsidt_serial_init(struct cyg_devtab_entry *tab)
{
    serial_channel *chan = (serial_channel *)tab->priv;
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
#ifdef CYGDBG_IO_INIT
    diag_printf("IDT SERIAL init - dev: %x.%d\n", mipsidt_chan->base, mipsidt_chan->int_num);
#endif
    (chan->callbacks->serial_init)(chan);  // Really only required for interrupt driven devices
    if (chan->out_cbuf.len != 0) {
        cyg_drv_interrupt_create(mipsidt_chan->int_num,
                                 0,         // can change IRQ0 priority
                                 (cyg_addrword_t)chan,   //  Data item passed to interrupt handler
                                 mipsidt_serial_ISR,
                                 mipsidt_serial_DSR,
                                 &mipsidt_chan->serial_interrupt_handle,
                                 &mipsidt_chan->serial_interrupt);
        cyg_drv_interrupt_attach(mipsidt_chan->serial_interrupt_handle);
        cyg_drv_interrupt_unmask(mipsidt_chan->int_num);
    }
    mipsidt_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 
mipsidt_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;
}

// Send a character to the device output buffer.
// Return 'true' if character is sent to device
static bool
mipsidt_serial_putc(serial_channel *chan, unsigned char c)
{
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
    cyg_addrword_t port = mipsidt_chan->base;
    cyg_uint8 _lsr;

    HAL_READ_UINT8(port+SER_16550_LSR, _lsr);
    if (((_lsr & (SIO_LSR_THRE | SIO_LSR_TEMT)) == 0x60)) {
        // Transmit buffer is empty
        HAL_WRITE_UINT8(port+SER_16550_THR, c);
        return true;
    } else {
        // No space
        return false;
    }
}

// Fetch a character from the device input buffer, waiting if necessary
static unsigned char 
mipsidt_serial_getc(serial_channel *chan)
{
    unsigned char c;
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
    cyg_addrword_t port = mipsidt_chan->base;
    cyg_uint8 _lsr;

    do {
        HAL_READ_UINT8(port+SER_16550_LSR, _lsr);
    } while ((_lsr & SIO_LSR_DR) == 0);
    HAL_READ_UINT8(port+SER_16550_RBR, c);
    return c;
}

// Set up the device characteristics; baud rate, etc.
static Cyg_ErrNo
mipsidt_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 != mipsidt_serial_config_port(chan, config, false) )
            return -EINVAL;
      }
      break;
    default:
        return -EINVAL;
    }
    return ENOERR;
}

// Enable the transmitter on the device
static void
mipsidt_serial_start_xmit(serial_channel *chan)
{
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
    cyg_addrword_t port = mipsidt_chan->base;
    cyg_uint8 _ier;

    HAL_READ_UINT8(port+SER_16550_IER, _ier);
    _ier |= IER_XMT;                    // Enable xmit interrupt
    HAL_WRITE_UINT8(port+SER_16550_IER, _ier);

    // We should not need to call this here.  THRE Interrupts are enabled, and the DSR
    // below calls this function.  However, sometimes we get called with Master Interrupts
    // disabled, and thus the DSR never runs.  This is unfortunate because it means we
    // will be doing multiple processing steps for the same thing.
    (chan->callbacks->xmt_char)(chan);
}

// Disable the transmitter on the device
static void 
mipsidt_serial_stop_xmit(serial_channel *chan)
{
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
    cyg_addrword_t port = mipsidt_chan->base;
    cyg_uint8 _ier;

    HAL_READ_UINT8(port+SER_16550_IER, _ier);
    _ier &= ~IER_XMT;                   // Disable xmit interrupt
    HAL_WRITE_UINT8(port+SER_16550_IER, _ier);
}

// Serial I/O - low level interrupt handler (ISR)
static cyg_uint32 
mipsidt_serial_ISR(cyg_vector_t vector, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;

    cyg_drv_interrupt_mask(mipsidt_chan->int_num);
    cyg_drv_interrupt_acknowledge(mipsidt_chan->int_num);
    return CYG_ISR_CALL_DSR;  // Cause DSR to be run
}

// Serial I/O - high level interrupt handler (DSR)
static void       
mipsidt_serial_DSR(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)
{
    serial_channel *chan = (serial_channel *)data;
    mipsidt_serial_info *mipsidt_chan = (mipsidt_serial_info *)chan->dev_priv;
    cyg_addrword_t port = mipsidt_chan->base;
    cyg_uint8 _iir;

    HAL_READ_UINT8(port+SER_16550_IIR, _iir);
    _iir &= SIO_IIR_ID_MASK;
    if ( ISR_Tx_Empty == _iir ) {
        (chan->callbacks->xmt_char)(chan);
    } else if (( ISR_Rx_Avail == _iir ) || ( ISR_Rx_Char_Timeout == _iir )) {
        cyg_uint8 _c;
        HAL_READ_UINT8(port+SER_16550_RBR, _c);
        (chan->callbacks->rcv_char)(chan, _c);
    }

    cyg_drv_interrupt_unmask(mipsidt_chan->int_num);
}

#endif

//-------------------------------------------------------------------------
// EOF mipsidt_serial.c