boot/serial_printk.c

#include

#include

#include

static int early_serial_base = 0x3f8;  /*ttyS0*/

#define XMTRDY 0x20

#define DLAB 0x80

#define TXR 0 /*Transmit register(WRITE)*/

#define RXR 0 /*Receive register(READ)*/

#define IER 1 /*Interrupt Enable*/

#define IIR 2 /*Interrupt ID*/

#define FCR 2 /*FIFO control*/

#define LCR 3 /*Line control*/

#define MCR 4 /*Modem control*/

#define LSR 5 /*Line Status*/

#define MSR 6 /*Modem Status*/

#define DLL 0 /*Divisor Latch Low*/

#define DLH 1 /*Divisor latch High*/

static int early_serial_putc(uint8_t ch)

{

uint16_t timeout = 0xffff;

while((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)

iodelay();

outb(early_serial_base + TXR, ch);

return timeout ? 0 : -1;

}

static void early_serial_write(const char *s, uint32_t n)

{

while(*s && n-- > 0)

{

if (*s == '\n')

early_serial_putc('\r');

early_serial_putc(*s);

s++;

}

}

int __printk(const char *file, int line, const char *fmt, ...)

{

int i;

char buf[512];

va_list args;

va_start(args, fmt);

//i = vsnprintf(buf, sizeof(buf), fmt, args);

i = vsprintf(buf, fmt, args);

va_end(args);

early_serial_write(buf, strlen(buf));

return i;

}

#define DEFAULT_BAUD 9600

void early_serial_init()

{

uint32_t port = 0;

uint8_t c;

uint32_t divisor;

uint32_t baud = DEFAULT_BAUD;

static const int bases[] = { 0x3f8, 0x2f8 };

early_serial_base = bases[port];

outb(early_serial_base + LCR, 0x3); /*8n1*/

outb(early_serial_base + IER, 0); /*no intr*/

outb(early_serial_base + FCR, 0); /*no fifo*/

outb(early_serial_base + MCR, 0x3); /*DTR+RTS*/

divisor = 115200 / baud;

c = inb(early_serial_base + LCR);

outb(early_serial_base + LCR, c | DLAB);

outb(early_serial_base + DLL, divisor & 0xff);

outb(early_serial_base + DLH, (divisor >> 8) & 0xff);

outb(early_serial_base + LCR, c & ~DLAB);

}