arch/x86/boot/early_serial_console.c

   1 #include "boot.h"
   2
   3 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
   4
   5 #define XMTRDY          0x20
   6
   7 #define DLAB            0x80
   8
   9 #define TXR             0       /*  Transmit register (WRITE) */
  10 #define RXR             0       /*  Receive register  (READ)  */
  11 #define IER             1       /*  Interrupt Enable          */
  12 #define IIR             2       /*  Interrupt ID              */
  13 #define FCR             2       /*  FIFO control              */
  14 #define LCR             3       /*  Line control              */
  15 #define MCR             4       /*  Modem control             */
  16 #define LSR             5       /*  Line Status               */
  17 #define MSR             6       /*  Modem Status              */
  18 #define DLL             0       /*  Divisor Latch Low         */
  19 #define DLH             1       /*  Divisor latch High        */
  20
  21 #define DEFAULT_BAUD 9600
  22
  23 static void early_serial_init(int port, int baud)
  24 {
  25         unsigned char c;
  26         unsigned divisor;
  27
  28         outb(0x3, port + LCR);  /* 8n1 */
  29         outb(0, port + IER);    /* no interrupt */
  30         outb(0, port + FCR);    /* no fifo */
  31         outb(0x3, port + MCR);  /* DTR + RTS */
  32
  33         divisor = 115200 / baud;
  34         c = inb(port + LCR);
  35         outb(c | DLAB, port + LCR);
  36         outb(divisor & 0xff, port + DLL);
  37         outb((divisor >> 8) & 0xff, port + DLH);
  38         outb(c & ~DLAB, port + LCR);
  39
  40         early_serial_base = port;
  41 }
  42
  43 static void parse_earlyprintk(void)
  44 {
  45         int baud = DEFAULT_BAUD;
  46         char arg[32];
  47         int pos = 0;
  48         int port = 0;
  49
  50         if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
  51                 char *e;
  52
  53                 if (!strncmp(arg, "serial", 6)) {
  54                         port = DEFAULT_SERIAL_PORT;
  55                         pos += 6;
  56                 }
  57
  58                 if (arg[pos] == ',')
  59                         pos++;
  60
  61                 /*
  62                  * make sure we have
  63                  *      "serial,0x3f8,115200"
  64                  *      "serial,ttyS0,115200"
  65                  *      "ttyS0,115200"
  66                  */
  67                 if (pos == 7 && !strncmp(arg + pos, "0x", 2)) {
  68                         port = simple_strtoull(arg + pos, &e, 16);
  69                         if (port == 0 || arg + pos == e)
  70                                 port = DEFAULT_SERIAL_PORT;
  71                         else
  72                                 pos = e - arg;
  73                 } else if (!strncmp(arg + pos, "ttyS", 4)) {
  74                         static const int bases[] = { 0x3f8, 0x2f8 };
  75                         int idx = 0;
  76
  77                         if (!strncmp(arg + pos, "ttyS", 4))
  78                                 pos += 4;
  79
  80                         if (arg[pos++] == '1')
  81                                 idx = 1;
  82
  83                         port = bases[idx];
  84                 }
  85
  86                 if (arg[pos] == ',')
  87                         pos++;
  88
  89                 baud = simple_strtoull(arg + pos, &e, 0);
  90                 if (baud == 0 || arg + pos == e)
  91                         baud = DEFAULT_BAUD;
  92         }
  93
  94         if (port)
  95                 early_serial_init(port, baud);
  96 }
  97
  98 #define BASE_BAUD (1843200/16)
  99 static unsigned int probe_baud(int port)
 100 {
 101         unsigned char lcr, dll, dlh;
 102         unsigned int quot;
 103
 104         lcr = inb(port + LCR);
 105         outb(lcr | DLAB, port + LCR);
 106         dll = inb(port + DLL);
 107         dlh = inb(port + DLH);
 108         outb(lcr, port + LCR);
 109         quot = (dlh << 8) | dll;
 110
 111         return BASE_BAUD / quot;
 112 }
 113
 114 static void parse_console_uart8250(void)
 115 {
 116         char optstr[64], *options;
 117         int baud = DEFAULT_BAUD;
 118         int port = 0;
 119
 120         /*
 121          * console=uart8250,io,0x3f8,115200n8
 122          * need to make sure it is last one console !
 123          */
 124         if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
 125                 return;
 126
 127         options = optstr;
 128
 129         if (!strncmp(options, "uart8250,io,", 12))
 130                 port = simple_strtoull(options + 12, &options, 0);
 131         else if (!strncmp(options, "uart,io,", 8))
 132                 port = simple_strtoull(options + 8, &options, 0);
 133         else
 134                 return;
 135
 136         if (options && (options[0] == ','))
 137                 baud = simple_strtoull(options + 1, &options, 0);
 138         else
 139                 baud = probe_baud(port);
 140
 141         if (port)
 142                 early_serial_init(port, baud);
 143 }
 144
 145 void console_init(void)
 146 {
 147         parse_earlyprintk();
 148
 149         if (!early_serial_base)
 150                 parse_console_uart8250();
 151 }