arch/x86_64/kernel/early_printk.c

   1 #include <linux/console.h>
   2 #include <linux/kernel.h>
   3 #include <linux/init.h>
   4 #include <linux/string.h>
   5 #include <asm/io.h>
   6 #include <asm/processor.h>
   7
   8 /* Simple VGA output */
   9
  10 #ifdef __i386__
  11 #define VGABASE         __pa(__PAGE_OFFSET + 0xb8000UL)
  12 #else
  13 #define VGABASE         0xffffffff800b8000UL
  14 #endif
  15
  16 #define MAX_YPOS        25
  17 #define MAX_XPOS        80
  18
  19 static int current_ypos = 1, current_xpos = 0;
  20
  21 static void early_vga_write(struct console *con, const char *str, unsigned n)
  22 {
  23         char c;
  24         int  i, k, j;
  25
  26         while ((c = *str++) != '\0' && n-- > 0) {
  27                 if (current_ypos >= MAX_YPOS) {
  28                         /* scroll 1 line up */
  29                         for (k = 1, j = 0; k < MAX_YPOS; k++, j++) {
  30                                 for (i = 0; i < MAX_XPOS; i++) {
  31                                         writew(readw(VGABASE + 2*(MAX_XPOS*k + i)),
  32                                                VGABASE + 2*(MAX_XPOS*j + i));
  33                                 }
  34                         }
  35                         for (i = 0; i < MAX_XPOS; i++)
  36                                 writew(0x720, VGABASE + 2*(MAX_XPOS*j + i));
  37                         current_ypos = MAX_YPOS-1;
  38                 }
  39                 if (c == '\n') {
  40                         current_xpos = 0;
  41                         current_ypos++;
  42                 } else if (c != '\r')  {
  43                         writew(((0x7 << 8) | (unsigned short) c),
  44                                VGABASE + 2*(MAX_XPOS*current_ypos +
  45                                                 current_xpos++));
  46                         if (current_xpos >= MAX_XPOS) {
  47                                 current_xpos = 0;
  48                                 current_ypos++;
  49                         }
  50                 }
  51         }
  52 }
  53
  54 static struct console early_vga_console = {
  55         .name =         "earlyvga",
  56         .write =        early_vga_write,
  57         .flags =        CON_PRINTBUFFER,
  58         .index =        -1,
  59 };
  60
  61 /* Serial functions loosely based on a similar package from Klaus P. Gerlicher */
  62
  63 int early_serial_base = 0x3f8;  /* ttyS0 */
  64
  65 #define XMTRDY          0x20
  66
  67 #define DLAB            0x80
  68
  69 #define TXR             0       /*  Transmit register (WRITE) */
  70 #define RXR             0       /*  Receive register  (READ)  */
  71 #define IER             1       /*  Interrupt Enable          */
  72 #define IIR             2       /*  Interrupt ID              */
  73 #define FCR             2       /*  FIFO control              */
  74 #define LCR             3       /*  Line control              */
  75 #define MCR             4       /*  Modem control             */
  76 #define LSR             5       /*  Line Status               */
  77 #define MSR             6       /*  Modem Status              */
  78 #define DLL             0       /*  Divisor Latch Low         */
  79 #define DLH             1       /*  Divisor latch High        */
  80
  81 static int early_serial_putc(unsigned char ch)
  82 {
  83         unsigned timeout = 0xffff;
  84         while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
  85                 cpu_relax();
  86         outb(ch, early_serial_base + TXR);
  87         return timeout ? 0 : -1;
  88 }
  89
  90 static void early_serial_write(struct console *con, const char *s, unsigned n)
  91 {
  92         while (*s && n-- > 0) {
  93                 early_serial_putc(*s);
  94                 if (*s == '\n')
  95                         early_serial_putc('\r');
  96                 s++;
  97         }
  98 }
  99
 100 #define DEFAULT_BAUD 9600
 101
 102 static __init void early_serial_init(char *opt)
 103 {
 104         unsigned char c;
 105         unsigned divisor;
 106         unsigned baud = DEFAULT_BAUD;
 107         char *s, *e;
 108
 109         if (*opt == ',')
 110                 ++opt;
 111
 112         s = strsep(&opt, ",");
 113         if (s != NULL) {
 114                 unsigned port;
 115                 if (!strncmp(s,"0x",2)) {
 116                         early_serial_base = simple_strtoul(s, &e, 16);
 117                 } else {
 118                         static int bases[] = { 0x3f8, 0x2f8 };
 119
 120                         if (!strncmp(s,"ttyS",4))
 121                                 s += 4;
 122                         port = simple_strtoul(s, &e, 10);
 123                         if (port > 1 || s == e)
 124                                 port = 0;
 125                         early_serial_base = bases[port];
 126                 }
 127         }
 128
 129         outb(0x3, early_serial_base + LCR);     /* 8n1 */
 130         outb(0, early_serial_base + IER);       /* no interrupt */
 131         outb(0, early_serial_base + FCR);       /* no fifo */
 132         outb(0x3, early_serial_base + MCR);     /* DTR + RTS */
 133
 134         s = strsep(&opt, ",");
 135         if (s != NULL) {
 136                 baud = simple_strtoul(s, &e, 0);
 137                 if (baud == 0 || s == e)
 138                         baud = DEFAULT_BAUD;
 139         }
 140
 141         divisor = 115200 / baud;
 142         c = inb(early_serial_base + LCR);
 143         outb(c | DLAB, early_serial_base + LCR);
 144         outb(divisor & 0xff, early_serial_base + DLL);
 145         outb((divisor >> 8) & 0xff, early_serial_base + DLH);
 146         outb(c & ~DLAB, early_serial_base + LCR);
 147 }
 148
 149 static struct console early_serial_console = {
 150         .name =         "earlyser",
 151         .write =        early_serial_write,
 152         .flags =        CON_PRINTBUFFER,
 153         .index =        -1,
 154 };
 155
 156 /* Direct interface for emergencies */
 157 struct console *early_console = &early_vga_console;
 158 static int early_console_initialized = 0;
 159
 160 void early_printk(const char *fmt, ...)
 161 {
 162         char buf[512];
 163         int n;
 164         va_list ap;
 165
 166         va_start(ap,fmt);
 167         n = vscnprintf(buf,512,fmt,ap);
 168         early_console->write(early_console,buf,n);
 169         va_end(ap);
 170 }
 171
 172 static int keep_early;
 173
 174 int __init setup_early_printk(char *opt)
 175 {
 176         char *space;
 177         char buf[256];
 178
 179         if (early_console_initialized)
 180                 return -1;
 181
 182         opt = strchr(opt, '=') + 1;
 183
 184         strlcpy(buf,opt,sizeof(buf));
 185         space = strchr(buf, ' ');
 186         if (space)
 187                 *space = 0;
 188
 189         if (strstr(buf,"keep"))
 190                 keep_early = 1;
 191
 192         if (!strncmp(buf, "serial", 6)) {
 193                 early_serial_init(buf + 6);
 194                 early_console = &early_serial_console;
 195         } else if (!strncmp(buf, "ttyS", 4)) {
 196                 early_serial_init(buf);
 197                 early_console = &early_serial_console;
 198         } else if (!strncmp(buf, "vga", 3)) {
 199                 early_console = &early_vga_console;
 200         } else {
 201                 early_console = NULL;
 202                 return -1;
 203         }
 204         early_console_initialized = 1;
 205         register_console(early_console);
 206         return 0;
 207 }
 208
 209 void __init disable_early_printk(void)
 210 {
 211         if (!early_console_initialized || !early_console)
 212                 return;
 213         if (!keep_early) {
 214                 printk("disabling early console\n");
 215                 unregister_console(early_console);
 216                 early_console_initialized = 0;
 217         } else {
 218                 printk("keeping early console\n");
 219         }
 220 }
 221
 222 __setup("earlyprintk=", setup_early_printk);