2 * Serial port routines for use during early boot reporting. This code is
3 * included from both the compressed kernel and the regular kernel.
7 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
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 */
23 #define DEFAULT_BAUD 9600
25 static void early_serial_init(int port, int baud)
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 */
35 divisor = 115200 / baud;
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);
42 early_serial_base = port;
45 static void parse_earlyprintk(void)
47 int baud = DEFAULT_BAUD;
52 if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
55 if (!strncmp(arg, "serial", 6)) {
56 port = DEFAULT_SERIAL_PORT;
65 * "serial,0x3f8,115200"
66 * "serial,ttyS0,115200"
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;
75 } else if (!strncmp(arg + pos, "ttyS", 4)) {
76 static const int bases[] = { 0x3f8, 0x2f8 };
79 /* += strlen("ttyS"); */
82 if (arg[pos++] == '1')
91 baud = simple_strtoull(arg + pos, &e, 0);
92 if (baud == 0 || arg + pos == e)
97 early_serial_init(port, baud);
100 #define BASE_BAUD (1843200/16)
101 static unsigned int probe_baud(int port)
103 unsigned char lcr, dll, dlh;
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;
113 return BASE_BAUD / quot;
116 static void parse_console_uart8250(void)
118 char optstr[64], *options;
119 int baud = DEFAULT_BAUD;
123 * console=uart8250,io,0x3f8,115200n8
124 * need to make sure it is last one console !
126 if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
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);
138 if (options && (options[0] == ','))
139 baud = simple_strtoull(options + 1, &options, 0);
141 baud = probe_baud(port);
144 early_serial_init(port, baud);
147 void console_init(void)
151 if (!early_serial_base)
152 parse_console_uart8250();