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early_printk.c

#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/screen_info.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/fcntl.h>
#include <asm/setup.h>
#include <xen/hvc-console.h>

/* Simple VGA output */
#define VGABASE         (__ISA_IO_base + 0xb8000)

static int max_ypos = 25, max_xpos = 80;
static int current_ypos = 25, current_xpos = 0;

static void early_vga_write(struct console *con, const char *str, unsigned n)
{
      char c;
      int  i, k, j;

      while ((c = *str++) != '\0' && n-- > 0) {
            if (current_ypos >= max_ypos) {
                  /* scroll 1 line up */
                  for (k = 1, j = 0; k < max_ypos; k++, j++) {
                        for (i = 0; i < max_xpos; i++) {
                              writew(readw(VGABASE+2*(max_xpos*k+i)),
                                     VGABASE + 2*(max_xpos*j + i));
                        }
                  }
                  for (i = 0; i < max_xpos; i++)
                        writew(0x720, VGABASE + 2*(max_xpos*j + i));
                  current_ypos = max_ypos-1;
            }
            if (c == '\n') {
                  current_xpos = 0;
                  current_ypos++;
            } else if (c != '\r')  {
                  writew(((0x7 << 8) | (unsigned short) c),
                         VGABASE + 2*(max_xpos*current_ypos +
                                    current_xpos++));
                  if (current_xpos >= max_xpos) {
                        current_xpos = 0;
                        current_ypos++;
                  }
            }
      }
}

static struct console early_vga_console = {
      .name =           "earlyvga",
      .write =    early_vga_write,
      .flags =    CON_PRINTBUFFER,
      .index =    -1,
};

/* Serial functions loosely based on a similar package from Klaus P. Gerlicher */

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(unsigned char ch)
{
      unsigned timeout = 0xffff;
      while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
            cpu_relax();
      outb(ch, early_serial_base + TXR);
      return timeout ? 0 : -1;
}

static void early_serial_write(struct console *con, const char *s, unsigned n)
{
      while (*s && n-- > 0) {
            if (*s == '\n')
                  early_serial_putc('\r');
            early_serial_putc(*s);
            s++;
      }
}

#define DEFAULT_BAUD 9600

static __init void early_serial_init(char *s)
{
      unsigned char c;
      unsigned divisor;
      unsigned baud = DEFAULT_BAUD;
      char *e;

      if (*s == ',')
            ++s;

      if (*s) {
            unsigned port;
            if (!strncmp(s,"0x",2)) {
                  early_serial_base = simple_strtoul(s, &e, 16);
            } else {
                  static int bases[] = { 0x3f8, 0x2f8 };

                  if (!strncmp(s,"ttyS",4))
                        s += 4;
                  port = simple_strtoul(s, &e, 10);
                  if (port > 1 || s == e)
                        port = 0;
                  early_serial_base = bases[port];
            }
            s += strcspn(s, ",");
            if (*s == ',')
                  s++;
      }

      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 */

      if (*s) {
            baud = simple_strtoul(s, &e, 0);
            if (baud == 0 || s == e)
                  baud = DEFAULT_BAUD;
      }

      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);
}

static struct console early_serial_console = {
      .name =           "earlyser",
      .write =    early_serial_write,
      .flags =    CON_PRINTBUFFER,
      .index =    -1,
};

/* Console interface to a host file on AMD's SimNow! */

static int simnow_fd;

enum {
      MAGIC1 = 0xBACCD00A,
      MAGIC2 = 0xCA110000,
      XOPEN = 5,
      XWRITE = 4,
};

static noinline long simnow(long cmd, long a, long b, long c)
{
      long ret;
      asm volatile("cpuid" :
                 "=a" (ret) :
                 "b" (a), "c" (b), "d" (c), "0" (MAGIC1), "D" (cmd + MAGIC2));
      return ret;
}

static void __init simnow_init(char *str)
{
      char *fn = "klog";
      if (*str == '=')
            fn = ++str;
      /* error ignored */
      simnow_fd = simnow(XOPEN, (unsigned long)fn, O_WRONLY|O_APPEND|O_CREAT, 0644);
}

static void simnow_write(struct console *con, const char *s, unsigned n)
{
      simnow(XWRITE, simnow_fd, (unsigned long)s, n);
}

static struct console simnow_console = {
      .name =           "simnow",
      .write =    simnow_write,
      .flags =    CON_PRINTBUFFER,
      .index =    -1,
};

/* Direct interface for emergencies */
struct console *early_console = &early_vga_console;
static int early_console_initialized = 0;

void early_printk(const char *fmt, ...)
{
      char buf[512];
      int n;
      va_list ap;

      va_start(ap,fmt);
      n = vscnprintf(buf,512,fmt,ap);
      early_console->write(early_console,buf,n);
      va_end(ap);
}

static int __initdata keep_early;

static int __init setup_early_printk(char *buf)
{
      if (!buf)
            return 0;

      if (early_console_initialized)
            return 0;
      early_console_initialized = 1;

      if (strstr(buf, "keep"))
            keep_early = 1;

      if (!strncmp(buf, "serial", 6)) {
            early_serial_init(buf + 6);
            early_console = &early_serial_console;
      } else if (!strncmp(buf, "ttyS", 4)) {
            early_serial_init(buf);
            early_console = &early_serial_console;
      } else if (!strncmp(buf, "vga", 3)
                 && boot_params.screen_info.orig_video_isVGA == 1) {
            max_xpos = boot_params.screen_info.orig_video_cols;
            max_ypos = boot_params.screen_info.orig_video_lines;
            current_ypos = boot_params.screen_info.orig_y;
            early_console = &early_vga_console;
      } else if (!strncmp(buf, "simnow", 6)) {
            simnow_init(buf + 6);
            early_console = &simnow_console;
            keep_early = 1;
#ifdef CONFIG_HVC_XEN
      } else if (!strncmp(buf, "xen", 3)) {
            early_console = &xenboot_console;
#endif
      }

      if (keep_early)
            early_console->flags &= ~CON_BOOT;
      else
            early_console->flags |= CON_BOOT;
      register_console(early_console);
      return 0;
}
early_param("earlyprintk", setup_early_printk);

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