ns16550.c

#include "ns16550.h"
#include "io.h"
#include <stdio.h>

#define PORT 0x3f8

#define REG_RBR 0		/* r */
#define REG_THR 0		/* w */
#define REG_DLL 0               /* w (dlab = 1) */
#define REG_DLM 1               /* w (dlab = 1) */
#define REG_IER 1		/* rw */
#define REG_FCR 2		/* w */
#define REG_IIR 2		/* r */
#define REG_LCR 3		/* rw */
#define REG_MCR 4		/* rw */
#define REG_LSR 5		/* rw */
#define REG_MSR 6		/* rw */
#define REG_SCR 7		/* rw */

#define FCR_FIFO_ENABLE (1<<0)
#define FCR_RESET_RCVR (1<<1)
#define FCR_RESET_XMIT (1<<2)
#define FCR_DMA_MODE_SELECT (1<<3)
#define FCR_RCVR_TRIGGER_TRIGGER_1 (0<<6)
#define FCR_RCVR_TRIGGER_TRIGGER_4 (1<<6)
#define FCR_RCVR_TRIGGER_TRIGGER_8 (2<<6)
#define FCR_RCVR_TRIGGER_TRIGGER_14 (3<<6)

#define IER_ERBFI (1<<0)
#define IER_ETBEI (1<<1)
#define IER_ELSI (1<<2)
#define IER_EDSSI (1<<3)

#define LSR_DR (1<<0)
#define LSR_OE (1<<1)
#define LSR_PE (1<<2)
#define LSR_FE (1<<3)
#define LSR_BI (1<<4)
#define LSR_THR (1<<5)
#define LSR_TEMT (1<<6)
#define LSR_ERROR_RCVR (1<<7)

#define LCR_WLS_5 (0<<0)
#define LCR_WLS_6 (1<<0)
#define LCR_WLS_7 (2<<0)
#define LCR_WLS_8 (3<<0)
#define LCR_STB2 (1<<2)
#define LCR_STB1 (0<<2)
#define LCR_PEN (1<<3)
#define LCR_EPS (1<<4)
#define LCR_STICK_PARITY (1<<5)
#define LCR_SET_BREAK (1<<6)
#define LCR_DLAB (1<<7)

void
ns16550_init(void)
{
        outb(PORT+REG_LCR, LCR_WLS_8|LCR_STB2);
        outb(PORT+REG_FCR, FCR_FIFO_ENABLE|FCR_RESET_RCVR|FCR_RESET_XMIT);

        /* set baud rate (115200) */
        outb(PORT+REG_LCR, LCR_DLAB);
        outb(PORT+REG_DLL, 0x01);
        outb(PORT+REG_DLM, 0x00);
        outb(PORT+REG_LCR, 0);

        outb(PORT+REG_LCR, LCR_WLS_8|LCR_STB1);
}

void
ns16550_write(const char *buffer, int n)
{
	int i;
	for (i=0; i<n; i++) {
		unsigned char c;

		while (! ((c=inb(PORT+REG_LSR)) & LSR_THR))
			;

		outb(PORT + REG_THR, buffer[i]);
		eieio();
	}
}

void
ns16550_read(char *buffer, int n)
{
	int i;
	for (i=0; i<n; i++) {
		unsigned char c;

		while (! ((c=inb(PORT+REG_LSR)) & LSR_DR))
			;

		eieio();
		buffer[i] = inb(PORT+REG_RBR);
	}
}

static const unsigned char hex_table[] = {
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
	'a', 'b', 'c', 'd', 'e', 'f'
};

void
ns16550_dump_registers(void)
{
	char buffer[3];
	unsigned char data;
	buffer[2] = '\0';

#define DUMP(x)					\
	data = inb(PORT+x);			\
	buffer[0] = hex_table[data>>4];		\
	buffer[1] = hex_table[data&0xf];	\
	puts(buffer);

	puts("LCR=");
	DUMP(REG_LCR);
	puts("IER=");
	DUMP(REG_IER);
	puts("IIR=");
	DUMP(REG_IIR);
	puts("LCR=");
	DUMP(REG_LCR);
	puts("MCR=");
	DUMP(REG_MCR);
	puts("LSR=");
	DUMP(REG_LSR);
	puts("MSR=");
	DUMP(REG_MSR);
	puts("SCR=");
	DUMP(REG_SCR);
}