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// Intel 8250 serial port (UART).
#include "types.h"
#include "defs.h"
#include "param.h"
#include "traps.h"
#include "spinlock.h"
#include "dev.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
#define COM1 0x3f8
static int uart; // is there a uart?
void
uartinit(void)
{
char *p;
// Turn off the FIFO
outb(COM1+2, 0);
// 9600 baud, 8 data bits, 1 stop bit, parity off.
outb(COM1+3, 0x80); // Unlock divisor
outb(COM1+0, 115200/9600);
outb(COM1+1, 0);
outb(COM1+3, 0x03); // Lock divisor, 8 data bits.
outb(COM1+4, 0);
outb(COM1+1, 0x01); // Enable receive interrupts.
// If status is 0xFF, no serial port.
if(inb(COM1+5) == 0xFF)
return;
uart = 1;
// Acknowledge pre-existing interrupt conditions;
// enable interrupts.
inb(COM1+2);
inb(COM1+0);
picenable(IRQ_COM1);
ioapicenable(IRQ_COM1, 0);
// Announce that we're here.
for(p="xv6...\n"; *p; p++)
uartputc(*p);
}
void
uartputc(int c)
{
int i;
if(!uart)
return;
for(i = 0; i < 128 && !(inb(COM1+5) & 0x20); i++)
microdelay(10);
outb(COM1+0, c);
}
static int
uartgetc(void)
{
if(!uart)
return -1;
if(!(inb(COM1+5) & 0x01))
return -1;
return inb(COM1+0);
}
void
uartintr(void)
{
consoleintr(uartgetc);
}
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