arch/x86/boot/early_serial_console.c

   1 /*
   2  * Serial port routines for use during early boot reporting. This code is
   3  * included from both the compressed kernel and the regular kernel.
   4  */
   5 #include "boot.h"
   6
   7 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
   8
   9 #define DLAB            0x80
  10
  11 #define TXR             0       /*  Transmit register (WRITE) */
  12 #define RXR             0       /*  Receive register  (READ)  */
  13 #define IER             1       /*  Interrupt Enable          */
  14 #define IIR             2       /*  Interrupt ID              */
  15 #define FCR             2       /*  FIFO control              */
  16 #define LCR             3       /*  Line control              */
  17 #define MCR             4       /*  Modem control             */
  18 #define LSR             5       /*  Line Status               */
  19 #define MSR             6       /*  Modem Status              */
  20 #define DLL             0       /*  Divisor Latch Low         */
  21 #define DLH             1       /*  Divisor latch High        */
  22
  23 #define DEFAULT_BAUD 9600
  24
  25 static void early_serial_init(int port, int baud)
  26 {
  27         unsigned char c;
  28         unsigned divisor;
  29
  30         outb(0x3, port + LCR);  /* 8n1 */
  31         outb(0, port + IER);    /* no interrupt */
  32         outb(0, port + FCR);    /* no fifo */
  33         outb(0x3, port + MCR);  /* DTR + RTS */
  34
  35         divisor = 115200 / baud;
  36         c = inb(port + LCR);
  37         outb(c | DLAB, port + LCR);
  38         outb(divisor & 0xff, port + DLL);
  39         outb((divisor >> 8) & 0xff, port + DLH);
  40         outb(c & ~DLAB, port + LCR);
  41
  42         early_serial_base = port;
  43 }
  44
  45 static void parse_earlyprintk(void)
  46 {
  47         int baud = DEFAULT_BAUD;
  48         char arg[32];
  49         int pos = 0;
  50         int port = 0;
  51
  52         if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
  53                 char *e;
  54
  55                 if (!strncmp(arg, "serial", 6)) {
  56                         port = DEFAULT_SERIAL_PORT;
  57                         pos += 6;
  58                 }
  59
  60                 if (arg[pos] == ',')
  61                         pos++;
  62
  63                 /*
  64                  * make sure we have
  65                  *      "serial,0x3f8,115200"
  66                  *      "serial,ttyS0,115200"
  67                  *      "ttyS0,115200"
  68                  */
  69                 if (pos == 7 && !strncmp(arg + pos, "0x", 2)) {
  70                         port = simple_strtoull(arg + pos, &e, 16);
  71                         if (port == 0 || arg + pos == e)
  72                                 port = DEFAULT_SERIAL_PORT;
  73                         else
  74                                 pos = e - arg;
  75                 } else if (!strncmp(arg + pos, "ttyS", 4)) {
  76                         static const int bases[] = { 0x3f8, 0x2f8 };
  77                         int idx = 0;
  78
  79                         /* += strlen("ttyS"); */
  80                         pos += 4;
  81
  82                         if (arg[pos++] == '1')
  83                                 idx = 1;
  84
  85                         port = bases[idx];
  86                 }
  87
  88                 if (arg[pos] == ',')
  89                         pos++;
  90
  91                 baud = simple_strtoull(arg + pos, &e, 0);
  92                 if (baud == 0 || arg + pos == e)
  93                         baud = DEFAULT_BAUD;
  94         }
  95
  96         if (port)
  97                 early_serial_init(port, baud);
  98 }
  99
 100 #define BASE_BAUD (1843200/16)
 101 static unsigned int probe_baud(int port)
 102 {
 103         unsigned char lcr, dll, dlh;
 104         unsigned int quot;
 105
 106         lcr = inb(port + LCR);
 107         outb(lcr | DLAB, port + LCR);
 108         dll = inb(port + DLL);
 109         dlh = inb(port + DLH);
 110         outb(lcr, port + LCR);
 111         quot = (dlh << 8) | dll;
 112
 113         return BASE_BAUD / quot;
 114 }
 115
 116 static void parse_console_uart8250(void)
 117 {
 118         char optstr[64], *options;
 119         int baud = DEFAULT_BAUD;
 120         int port = 0;
 121
 122         /*
 123          * console=uart8250,io,0x3f8,115200n8
 124          * need to make sure it is last one console !
 125          */
 126         if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
 127                 return;
 128
 129         options = optstr;
 130
 131         if (!strncmp(options, "uart8250,io,", 12))
 132                 port = simple_strtoull(options + 12, &options, 0);
 133         else if (!strncmp(options, "uart,io,", 8))
 134                 port = simple_strtoull(options + 8, &options, 0);
 135         else
 136                 return;
 137
 138         if (options && (options[0] == ','))
 139                 baud = simple_strtoull(options + 1, &options, 0);
 140         else
 141                 baud = probe_baud(port);
 142
 143         if (port)
 144                 early_serial_init(port, baud);
 145 }
 146
 147 void console_init(void)
 148 {
 149         parse_earlyprintk();
 150
 151         if (!early_serial_base)
 152                 parse_console_uart8250();
 153 }