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fa97bdf927
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: Pekka Enberg <penberg@cs.helsinki.fi> LKML-Reference: <1278835617-11368-1-git-send-email-penberg@cs.helsinki.fi> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
214 lines
4.3 KiB
C
214 lines
4.3 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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* Copyright 2009 Intel Corporation; author H. Peter Anvin
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* Very simple screen and serial I/O
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*/
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#include "boot.h"
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#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
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static int early_serial_base;
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#define XMTRDY 0x20
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#define DLAB 0x80
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#define TXR 0 /* Transmit register (WRITE) */
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#define RXR 0 /* Receive register (READ) */
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#define IER 1 /* Interrupt Enable */
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#define IIR 2 /* Interrupt ID */
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#define FCR 2 /* FIFO control */
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#define LCR 3 /* Line control */
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#define MCR 4 /* Modem control */
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#define LSR 5 /* Line Status */
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#define MSR 6 /* Modem Status */
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#define DLL 0 /* Divisor Latch Low */
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#define DLH 1 /* Divisor latch High */
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#define DEFAULT_BAUD 9600
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/*
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* These functions are in .inittext so they can be used to signal
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* error during initialization.
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*/
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static void __attribute__((section(".inittext"))) serial_putchar(int ch)
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{
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unsigned timeout = 0xffff;
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while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
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cpu_relax();
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outb(ch, early_serial_base + TXR);
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}
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static void __attribute__((section(".inittext"))) bios_putchar(int ch)
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{
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struct biosregs ireg;
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initregs(&ireg);
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ireg.bx = 0x0007;
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ireg.cx = 0x0001;
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ireg.ah = 0x0e;
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ireg.al = ch;
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intcall(0x10, &ireg, NULL);
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}
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void __attribute__((section(".inittext"))) putchar(int ch)
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{
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if (ch == '\n')
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putchar('\r'); /* \n -> \r\n */
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bios_putchar(ch);
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if (early_serial_base != 0)
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serial_putchar(ch);
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}
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void __attribute__((section(".inittext"))) puts(const char *str)
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{
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while (*str)
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putchar(*str++);
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}
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/*
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* Read the CMOS clock through the BIOS, and return the
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* seconds in BCD.
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*/
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static u8 gettime(void)
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{
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struct biosregs ireg, oreg;
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initregs(&ireg);
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ireg.ah = 0x02;
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intcall(0x1a, &ireg, &oreg);
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return oreg.dh;
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}
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/*
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* Read from the keyboard
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*/
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int getchar(void)
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{
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struct biosregs ireg, oreg;
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initregs(&ireg);
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/* ireg.ah = 0x00; */
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intcall(0x16, &ireg, &oreg);
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return oreg.al;
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}
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static int kbd_pending(void)
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{
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struct biosregs ireg, oreg;
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initregs(&ireg);
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ireg.ah = 0x01;
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intcall(0x16, &ireg, &oreg);
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return !(oreg.eflags & X86_EFLAGS_ZF);
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}
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void kbd_flush(void)
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{
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for (;;) {
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if (!kbd_pending())
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break;
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getchar();
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}
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}
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int getchar_timeout(void)
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{
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int cnt = 30;
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int t0, t1;
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t0 = gettime();
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while (cnt) {
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if (kbd_pending())
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return getchar();
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t1 = gettime();
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if (t0 != t1) {
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cnt--;
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t0 = t1;
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}
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}
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return 0; /* Timeout! */
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}
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static void early_serial_init(int baud)
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{
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unsigned char c;
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unsigned divisor;
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outb(0x3, early_serial_base + LCR); /* 8n1 */
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outb(0, early_serial_base + IER); /* no interrupt */
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outb(0, early_serial_base + FCR); /* no fifo */
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outb(0x3, early_serial_base + MCR); /* DTR + RTS */
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divisor = 115200 / baud;
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c = inb(early_serial_base + LCR);
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outb(c | DLAB, early_serial_base + LCR);
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outb(divisor & 0xff, early_serial_base + DLL);
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outb((divisor >> 8) & 0xff, early_serial_base + DLH);
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outb(c & ~DLAB, early_serial_base + LCR);
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}
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void console_init(void)
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{
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int baud = DEFAULT_BAUD;
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char arg[32];
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int pos = 0;
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if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
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char *e;
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if (!strncmp(arg, "serial", 6)) {
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early_serial_base = DEFAULT_SERIAL_PORT;
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pos += 6;
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}
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if (arg[pos] == ',')
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pos++;
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if (!strncmp(arg, "ttyS", 4)) {
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static const int bases[] = { 0x3f8, 0x2f8 };
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int port = 0;
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if (!strncmp(arg + pos, "ttyS", 4))
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pos += 4;
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if (arg[pos++] == '1')
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port = 1;
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early_serial_base = bases[port];
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}
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if (arg[pos] == ',')
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pos++;
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baud = simple_strtoull(arg + pos, &e, 0);
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if (baud == 0 || arg + pos == e)
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baud = DEFAULT_BAUD;
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}
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if (early_serial_base != 0)
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early_serial_init(baud);
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}
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