ref: 9f76a7f6819ac04552b4fb6588156f3e4089d1d7
dir: /os/pc/i8250.c/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "io.h"
#include "../port/error.h"
/*
* INS8250 uart
*/
enum
{
/*
* register numbers
*/
Data= 0, /* xmit/rcv buffer */
Iena= 1, /* interrupt enable */
Ircv= (1<<0), /* for char rcv'd */
Ixmt= (1<<1), /* for xmit buffer empty */
Irstat=(1<<2), /* for change in rcv'er status */
Imstat=(1<<3), /* for change in modem status */
Istat= 2, /* interrupt flag (read) */
Fenabd=(3<<6), /* on if fifo's enabled */
Fifoctl=2, /* fifo control (write) */
Fena= (1<<0), /* enable xmit/rcv fifos */
Ftrig= (1<<6), /* trigger after 4 input characters */
Fclear=(3<<1), /* clear xmit & rcv fifos */
Format= 3, /* byte format */
Bits8= (3<<0), /* 8 bits/byte */
Stop2= (1<<2), /* 2 stop bits */
Pena= (1<<3), /* generate parity */
Peven= (1<<4), /* even parity */
Pforce=(1<<5), /* force parity */
Break= (1<<6), /* generate a break */
Dra= (1<<7), /* address the divisor */
Mctl= 4, /* modem control */
Dtr= (1<<0), /* data terminal ready */
Rts= (1<<1), /* request to send */
Ri= (1<<2), /* ring */
Inton= (1<<3), /* turn on interrupts */
Loop= (1<<4), /* loop back */
Lstat= 5, /* line status */
Inready=(1<<0), /* receive buffer full */
Oerror=(1<<1), /* receiver overrun */
Perror=(1<<2), /* receiver parity error */
Ferror=(1<<3), /* rcv framing error */
Outready=(1<<5), /* output buffer empty */
Mstat= 6, /* modem status */
Ctsc= (1<<0), /* clear to send changed */
Dsrc= (1<<1), /* data set ready changed */
Rire= (1<<2), /* rising edge of ring indicator */
Dcdc= (1<<3), /* data carrier detect changed */
Cts= (1<<4), /* complement of clear to send line */
Dsr= (1<<5), /* complement of data set ready line */
Ring= (1<<6), /* complement of ring indicator line */
Dcd= (1<<7), /* complement of data carrier detect line */
Scratch=7, /* scratchpad */
Dlsb= 0, /* divisor lsb */
Dmsb= 1, /* divisor msb */
Serial= 0,
Modem= 1,
};
typedef struct Uart Uart;
struct Uart
{
int port;
uchar sticky[8]; /* sticky write register values */
int nofifo;
void (*rx)(int); /* routine to take a received character */
int (*tx)(void); /* routine to get a character to transmit */
ulong frame;
ulong overrun;
};
static Uart i8250uart[1];
#define UartFREQ 1843200
#define i8250regw(u, r, v) outb((u)->port+(r), (u)->sticky[(r)]|(v))
#define i8250regr(u, r) inb((u)->port+(r))
/*
* set the baud rate by calculating and setting the baudrate
* generator constant. This will work with fairly non-standard
* baud rates.
*/
static void
i8250setbaud(Uart* uart, int rate)
{
ulong brconst;
brconst = (UartFREQ+8*rate-1)/(16*rate);
i8250regw(uart, Format, Dra);
outb(uart->port+Dmsb, (brconst>>8) & 0xff);
outb(uart->port+Dlsb, brconst & 0xff);
i8250regw(uart, Format, 0);
}
/*
* toggle DTR
*/
static void
i8250dtr(Uart* uart, int n)
{
if(n)
uart->sticky[Mctl] |= Dtr;
else
uart->sticky[Mctl] &= ~Dtr;
i8250regw(uart, Mctl, 0);
}
/*
* toggle RTS
*/
static void
i8250rts(Uart* uart, int n)
{
if(n)
uart->sticky[Mctl] |= Rts;
else
uart->sticky[Mctl] &= ~Rts;
i8250regw(uart, Mctl, 0);
}
/*
* Enable/disable FIFOs (if possible).
*/
static void
i8250fifo(Uart* uart, int n)
{
int i, s;
if(uart->nofifo)
return;
s = splhi();
/* reset fifos */
i8250regw(uart, Fifoctl, Fclear);
/* empty buffer and interrupt conditions */
for(i = 0; i < 16; i++){
if(i8250regr(uart, Istat))
{}
if(i8250regr(uart, Data))
{}
}
/* turn on fifo */
if(n){
i8250regw(uart, Fifoctl, Fena|Ftrig);
if((i8250regr(uart, Istat) & Fenabd) == 0){
/* didn't work, must be an earlier chip type */
uart->nofifo = 1;
}
}
splx(s);
}
#ifdef notdef
static void
i8250intr(Ureg*, void* arg)
{
Uart *uart;
int ch;
int s, l, loops;
uart = arg;
for(loops = 0; loops < 1024; loops++){
s = i8250regr(uart, Istat);
switch(s & 0x3F){
case 6: /* receiver line status */
l = i8250regr(uart, Lstat);
if(l & Ferror)
uart->frame++;
if(l & Oerror)
uart->overrun++;
break;
case 4: /* received data available */
case 12:
ch = inb(uart->port+Data);
if(uart->rx)
(*uart->rx)(ch & 0x7F);
break;
case 2: /* transmitter empty */
ch = -1;
if(uart->tx)
ch = (*uart->tx)();
if(ch != -1)
outb(uart->port+Data, ch);
break;
case 0: /* modem status */
i8250regr(uart, Mstat);
break;
default:
if(s&1)
return;
print("weird modem interrupt #%2.2ux\n", s);
break;
}
}
panic("i8250intr: 0x%2.2ux\n", i8250regr(uart, Istat));
}
#endif /* notdef */
/*
* turn on a port's interrupts. set DTR and RTS
*/
static void
i8250enable(Uart* uart)
{
/*
* turn on interrupts
*/
uart->sticky[Iena] = 0;
#ifdef notdef
if(uart->tx)
uart->sticky[Iena] |= Ixmt;
if(uart->rx)
uart->sticky[Iena] |= Ircv|Irstat;
#endif /* notdef */
/*
* turn on DTR and RTS
*/
i8250dtr(uart, 1);
i8250rts(uart, 1);
i8250fifo(uart, 1);
i8250regw(uart, Iena, 0);
}
void
i8250special(int port, void (*rx)(int), int (*tx)(void), int baud)
{
Uart *uart = &i8250uart[0];
if(uart->port)
return;
switch(port){
case 0:
uart->port = 0x3F8;
#ifdef notdef
intrenable(VectorUART0, i8250intr, uart, BUSUNKNOWN);
#endif /* notdef */
break;
case 1:
uart->port = 0x2F8;
#ifdef notdef
intrenable(VectorUART1, i8250intr, uart, BUSUNKNOWN);
#endif /* notdef */
break;
default:
return;
}
/*
* set rate to 9600 baud.
* 8 bits/character.
* 1 stop bit.
* interrupts enabled.
*/
i8250setbaud(uart, 9600);
uart->sticky[Format] = Bits8;
i8250regw(uart, Format, 0);
uart->sticky[Mctl] |= Inton;
i8250regw(uart, Mctl, 0x0);
uart->rx = rx;
uart->tx = tx;
i8250enable(uart);
if(baud)
i8250setbaud(uart, baud);
}
int
i8250getc(void)
{
Uart *uart = &i8250uart[0];
if(i8250regr(uart, Lstat) & Inready)
return inb(uart->port+Data);
return 0;
}
void
i8250putc(int c)
{
Uart *uart = &i8250uart[0];
int i;
for(i = 0; i < 100; i++){
if(i8250regr(uart, Lstat) & Outready)
break;
delay(1);
}
outb(uart->port+Data, c);
}
void
i8250puts(char* s, int n)
{
int x;
x = splhi();
while(n--){
if(*s == '\n')
i8250putc('\r');
i8250putc(*s++);
}
splx(x);
}