ns16550.c

MIPS处理器的bootloader,龙芯就是用的修改过的PMON2

#include <termio.h>
#include <machine/bus.h>
#include "target/ns16550.h"

#include <pmon.h>

extern int getbaudval __P((int));

int ns16550 __P((int, char *, int, int));


static int
nsinit (volatile ns16550dev *dp, int chan)
{
#if 0
static int nsfifo;
    unsigned int x;

    /* force access to id reg */
    outb(&dp->cfcr,0);
    outb(&dp->iir, 0);
    if ((inb(&dp->iir) & 0x38) != 0) {
	return 1;
    }

    /* in case it really is a 16550, enable the fifos */
    outb(&dp->fifo, FIFO_ENABLE);
    for(x = 0; x < 1000000; x++);
    outb(&dp->fifo, FIFO_ENABLE | FIFO_RCV_RST | FIFO_XMT_RST | FIFO_TRIGGER_1);
    for(x = 0; x < 1000000; x++);

    if ((inb(&dp->iir) & IIR_FIFO_MASK) == IIR_FIFO_MASK)
	nsfifo = 1;
    else {
	dp->fifo = 0;
    }
#endif

    return 0;
}


static int
nsprogram (volatile ns16550dev *dp, int chan, int baudrate)
{
#if 0
    unsigned short brtc;
    int timeout;

    /* wait for Tx fifo to completely drain */
    timeout = 10000;
    while (!(inb(&dp->lsr) & LSR_TSRE))
	if (--timeout == 0)
	    break;

    baudrate = getbaudval (baudrate);
    if (baudrate == 0)
      return 1;

    brtc = BRTC (baudrate);

    outb(&dp->cfcr, CFCR_DLAB);
    outb(&dp->data, brtc & 0xff);
    outb(&dp->ier, brtc >> 8);
    outb(&dp->cfcr, CFCR_8BITS);
#if 0
    outb(&dp->mcr, MCR_DTR | MCR_RTS | MCR_IENABLE);
#endif
    outb(&dp->ier, 0);
#endif
    return 0;
}


int
ns16550 (int op, char *dat, int chan, int data)
{
    volatile ns16550dev *dp = (ns16550dev *) dat;

    if (chan > 0)
	return 1;

    switch (op) {
    case OP_INIT:
	return nsinit (dp, chan);

    case OP_XBAUD:
    case OP_BAUD:
	return nsprogram (dp, chan, data);

    case OP_TXRDY:
	return (inb(&dp->lsr) & LSR_TXRDY);

    case OP_TX:
	outb(&dp->data, data);
	break;

    case OP_RXRDY:
	return (inb(&dp->lsr) & LSR_RXRDY);

    case OP_RX:
	return inb(&dp->data) & 0xff;

    case OP_RXSTOP:
	if (data)
	    outb(&dp->mcr, inb(&dp->mcr) & ~MCR_RTS);	/* disable Rx */
	else
	    outb(&dp->mcr, inb(&dp->mcr) | MCR_RTS);	/* enable Rx */
	break;
    }
    return 0;
}