p16550.c

mips架构的bootloader,99左右的版本 但源代码现在没人更新了

/*************************************************************
 * File: lib/p16550.c
 * Purpose: Driver for 16550D UART
 * Author: Phil Bunce ([e-mail])
 * Revision History:
 *	980615	Created
 *	980618	Added OP_BAUDRATES
 *	981106	Works with "-board bdmr4102"
 */

#include <mips.h>
/* 
 * Polled I/O routines for the National NS16550 UART
 *
 */

#include <terms.h>
#include <utypes.h>


/* btab = sysclk/(baudrate*N)  */
/* btab = 14.7456MHz/(baudrate*16) */
static long btab_14[] = {
	-1, 	/* B0 */
	-1,	/* B50 */
	-1,	/* B75 */
	-1,	/* B110 */
	-1,	/* B134 */
	6144,	/* B150 */
	4608,	/* B200 */
	3072,	/* B300 */
	1536,	/* B600 */
	768,	/* B1200 */
	512,	/* B1800 */
	384,	/* B2400 */
	192,	/* B4800 */
	96,	/* B9600 */
	48,	/* B19200 */
	24,	/* B38400 */
	16,	/* B57600 */
	12,	/* B76800 */
	8,	/* B115200 */
	6,	/* B153600 */
	4,	/* B230400 */
	3,	/* B307200 */
	2,	/* B460800 */
	1,	/* B921600 */
	0	/* end */
	};

/* assumes a 18.432 MHz crystal is in use */
static long btab_18[] = {
	-1, 	/* B0 */
	23040,	/* B50 */
	15360,	/* B75 */
	10473,	/* B110 */
	8565,	/* B134 */
	7680,	/* B150 */
	-1,	/* B200 */
	3840,	/* B300 */
	1920,	/* B600 */
	960,	/* B1200 */
	640,	/* B1800 */
	480,	/* B2400 */
	240,	/* B4800 */
	120,	/* B9600 */
	60,	/* B19200 */
	30,	/* B38400 */
	20,	/* B57600 */
	-1,	/* B76800 */
	10,	/* B115200 */
	-1,	/* B153600 */
	5,	/* B230400 */
	-1,	/* B307200 */
	2,	/* B460800 */
	-1,	/* B921600 */
	0	/* end */
	};

#define DEFRATE		13 /* default baudrate (9600) */

#define inb(a)      (*((volatile Uchar *)(a)))
#define inh(a)      (*((volatile Ushort *)(a)))
#define outb(a,v)      (*((volatile Uchar *)(a))=(v))
#define outh(a,v)      (*((volatile Ushort *)(a))=(v))
#define outw(a,v)      (*((volatile Ulong *)(a))=(v))

#define RXRDY	0x01
#define TXRDY	0x20

#define STATUS	(gap*5)
#define RXHR	(gap*0)
#define TXHR	(gap*0)

/* ------- Registers ------------
        Read            Write
	---------------------
0	RHR		THR
1 	--- int_enable -----
2	int_ident 	FIFO cntrl
3 	---- line cntrl ----
4	---- modem ctrl ----
5	---- line status ---  01=rxrdy 20=txrdy
6	--- modem status ---
7	----- scratch ------
0+dlab	- ls divisor latch -
1+dlab	- ms divisor latch -
---------------------------------- */

/*************************************************************
*  p16550(op,siodat,chan,ch)
*/
p16550(op,siodat,chan,ch)
int op,chan,ch;
void *siodat;
{
int i,brate;
struct p16550Rec *info = siodat;
Ulong base = info->base;
int gap = info->gap;
Ulong m,v;
long *btab;

#ifdef MIPSEB
base += info->beoffs;
#endif

if (info->baudclk == 14) btab = btab_14;
else btab = btab_18;

switch (op) {
	case OP_RXRDY : 
		if (inb(base+STATUS)&RXRDY) return(1);
		break;

	case OP_RX :
		return inb(base+RXHR);

	case OP_TXRDY :
		if (inb(base+STATUS)&TXRDY) return(1);
		break;

	case OP_TX :
		outb(base+TXHR,ch);
		break;

	case OP_INIT : 
		/* set DLAB */
		outb(base+(3*gap),0x80);
		/* ms baud */
		outb(base+(1*gap),btab[DEFRATE]>>8); 
		/* ls baud */
		outb(base+(0*gap),btab[DEFRATE]&0xff);
		/* mode: 2 stopbits, no parity, 8 bitsdata */
		outb(base+(3*gap),0x03);
		break;
	case OP_BAUD : 
		brate = ch;
		/* check brate <= 23 */
		if (brate > 23) return(1); /* baud rate too large */
		/* return if unsupported baud rate */
		if (btab[brate] == -1) return(1);  
		outb(base+(3*gap),0x80);
		/* ms baud */
		outb(base+(1*gap),btab[brate]>>8); 
		/* ls baud */
		outb(base+(0*gap),btab[brate]&0xff);
		/* mode: 2 stopbits, no parity, 8 bitsdata */
		outb(base+(3*gap),0x03);
		break;
	case OP_CLKINIT : break;
	case OP_DELAY : return(0); break;
	case OP_BAUDRATES :
		m = 1;
		for (i=v=0;btab[i];i++) {
			if (btab[i] != -1) v |= m;
			m <<= 1;
			}
		return(v);
		break;
	}
return(0);
}