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Commit fa97bdf9 authored by Pekka Enberg's avatar Pekka Enberg Committed by H. Peter Anvin
Browse files

x86, setup: Early-boot serial I/O support 



This patch adds serial I/O support to the real-mode setup (very early
boot) printf(). It's useful for debugging boot code when running Linux
under KVM, for example. The actual code was lifted from early printk.

Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
LKML-Reference: <1278835617-11368-1-git-send-email-penberg@cs.helsinki.fi>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 589643be

arch/x86/boot/boot.h

+16 −0
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ 
extern struct setup_header hdr;

extern struct boot_params boot_params;



#define cpu_relax()	asm volatile("rep; nop")



/* Basic port I/O */

static inline void outb(u8 v, u16 port)

{
@@ -203,6 +205,17 @@ static inline int isdigit(int ch) 
	return (ch >= '0') && (ch <= '9');

}



static inline int isxdigit(int ch)

{

	if (isdigit(ch))

		return true;



	if ((ch >= 'a') && (ch <= 'f'))

		return true;



	return (ch >= 'A') && (ch <= 'F');

}



/* Heap -- available for dynamic lists. */

extern char _end[];

extern char *HEAP;
@@ -329,10 +342,13 @@ void initregs(struct biosregs *regs); 


/* string.c */

int strcmp(const char *str1, const char *str2);

int strncmp(const char *cs, const char *ct, size_t count);

size_t strnlen(const char *s, size_t maxlen);

unsigned int atou(const char *s);

unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base);



/* tty.c */

void console_init(void);

void puts(const char *);

void putchar(int);

int getchar(void);

arch/x86/boot/main.c

+3 −0
Original line number Diff line number Diff line
@@ -130,6 +130,9 @@ void main(void) 
	/* First, copy the boot header into the "zeropage" */

	copy_boot_params();



	/* Initialize the early-boot console */

	console_init();



	/* End of heap check */

	init_heap();

arch/x86/boot/string.c

+41 −0
Original line number Diff line number Diff line
@@ -30,6 +30,22 @@ int strcmp(const char *str1, const char *str2) 
	return 0;

}



int strncmp(const char *cs, const char *ct, size_t count)

{

	unsigned char c1, c2;



	while (count) {

		c1 = *cs++;

		c2 = *ct++;

		if (c1 != c2)

			return c1 < c2 ? -1 : 1;

		if (!c1)

			break;

		count--;

	}

	return 0;

}



size_t strnlen(const char *s, size_t maxlen)

{

	const char *es = s;
@@ -48,3 +64,28 @@ unsigned int atou(const char *s) 
		i = i * 10 + (*s++ - '0');

	return i;

}



/* Works only for digits and letters, but small and fast */

#define TOLOWER(x) ((x) | 0x20)



unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)

{

	unsigned long long result = 0;



	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')

		cp += 2;



	while (isxdigit(*cp)) {

		unsigned int value;



		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;

		if (value >= base)

			break;

		result = result * base + value;

		cp++;

	}

	if (endp)

		*endp = (char *)cp;



	return result;

}

arch/x86/boot/tty.c

+105 −6
Original line number Diff line number Diff line
@@ -10,23 +10,51 @@ 
 * ----------------------------------------------------------------------- */



/*

 * Very simple screen I/O

 * XXX: Probably should add very simple serial I/O?

 * Very simple screen and serial I/O

 */



#include "boot.h"



#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */



static int	early_serial_base;



#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        */



#define DEFAULT_BAUD 9600



/*

 * These functions are in .inittext so they can be used to signal

 * error during initialization.

 */



void __attribute__((section(".inittext"))) putchar(int ch)

static void __attribute__((section(".inittext"))) serial_putchar(int ch)

{

	struct biosregs ireg;

	unsigned timeout = 0xffff;



	if (ch == '\n')

		putchar('\r');	/* \n -> \r\n */

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

		cpu_relax();



	outb(ch, early_serial_base + TXR);

}



static void __attribute__((section(".inittext"))) bios_putchar(int ch)

{

	struct biosregs ireg;



	initregs(&ireg);

	ireg.bx = 0x0007;
@@ -36,6 +64,17 @@ void __attribute__((section(".inittext"))) putchar(int ch) 
	intcall(0x10, &ireg, NULL);

}



void __attribute__((section(".inittext"))) putchar(int ch)

{

	if (ch == '\n')

		putchar('\r');	/* \n -> \r\n */



	bios_putchar(ch);



	if (early_serial_base != 0)

		serial_putchar(ch);

}



void __attribute__((section(".inittext"))) puts(const char *str)

{

	while (*str)
@@ -112,3 +151,63 @@ int getchar_timeout(void) 


	return 0;		/* Timeout! */

}



static void early_serial_init(int baud)

{

	unsigned char c;

	unsigned divisor;



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

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

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

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



	divisor	= 115200 / baud;

	c = inb(early_serial_base + LCR);

	outb(c | DLAB, early_serial_base + LCR);

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

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

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

}



void console_init(void)

{

	int baud = DEFAULT_BAUD;

	char arg[32];

	int pos = 0;



	if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {

		char *e;



		if (!strncmp(arg, "serial", 6)) {

			early_serial_base = DEFAULT_SERIAL_PORT;

			pos += 6;

		}



		if (arg[pos] == ',')

			pos++;



		if (!strncmp(arg, "ttyS", 4)) {

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

			int port = 0;



			if (!strncmp(arg + pos, "ttyS", 4))

				pos += 4;



			if (arg[pos++] == '1')

				port = 1;



			early_serial_base = bases[port];

		}



		if (arg[pos] == ',')

			pos++;



		baud = simple_strtoull(arg + pos, &e, 0);

		if (baud == 0 || arg + pos == e)

			baud = DEFAULT_BAUD;

	}



	if (early_serial_base != 0)

		early_serial_init(baud);

}