early_printk.c

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#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/screen_info.h>
#include <linux/usb/ch9.h>
#include <linux/pci_regs.h>
#include <linux/pci_ids.h>
#include <linux/errno.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/fcntl.h>
#include <asm/setup.h>
#include <xen/hvc-console.h>
#include <asm/pci-direct.h>
#include <asm/fixmap.h>
#include <asm/mrst.h>
#include <asm/pgtable.h>
#include <linux/usb/ehci_def.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;

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;
        }
#ifdef CONFIG_KGDB_KDB
        if (c == '\b') {
            if (current_xpos > 0)
                current_xpos--;
        } else if (c == '\r') {
            current_xpos = 0;
        } else
#endif
        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 const int __initconst 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,
};

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

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

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

static inline void early_console_register(struct console *con, int keep_early)
{
    if (early_console->index != -1) {
        printk(KERN_CRIT "ERROR: earlyprintk= %s already used\n",
               con->name);
        return;
    }
    early_console = con;
    if (keep_early)
        early_console->flags &= ~CON_BOOT;
    else
        early_console->flags |= CON_BOOT;
    register_console(early_console);
}

static int __init setup_early_printk(char *buf)
{
    int keep;

    if (!buf)
        return 0;

    if (early_console_initialized)
        return 0;
    early_console_initialized = 1;

    keep = (strstr(buf, "keep") != NULL);

    while (*buf != '\0') {
        if (!strncmp(buf, "serial", 6)) {
            buf += 6;
            early_serial_init(buf);
            early_console_register(&early_serial_console, keep);
            if (!strncmp(buf, ",ttyS", 5))
                buf += 5;
        }
        if (!strncmp(buf, "ttyS", 4)) {
            early_serial_init(buf + 4);
            early_console_register(&early_serial_console, keep);
        }
        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_register(&early_vga_console, keep);
        }
#ifdef CONFIG_EARLY_PRINTK_DBGP
        if (!strncmp(buf, "dbgp", 4) && !early_dbgp_init(buf + 4))
            early_console_register(&early_dbgp_console, keep);
#endif
#ifdef CONFIG_HVC_XEN
        if (!strncmp(buf, "xen", 3))
            early_console_register(&xenboot_console, keep);
#endif
#ifdef CONFIG_EARLY_PRINTK_INTEL_MID
        if (!strncmp(buf, "mrst", 4)) {
            mrst_early_console_init();
            early_console_register(&early_mrst_console, keep);
        }

        if (!strncmp(buf, "hsu", 3)) {
            hsu_early_console_init(buf + 3);
            early_console_register(&early_hsu_console, keep);
        }
#endif
        buf++;
    }
    return 0;
}

early_param("earlyprintk", setup_early_printk);