3 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
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 */
21 #define DEFAULT_BAUD 9600
23 static void early_serial_init(int port, int baud)
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 */
33 divisor = 115200 / baud;
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);
40 early_serial_base = port;
43 static void parse_earlyprintk(void)
45 int baud = DEFAULT_BAUD;
50 if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
53 if (!strncmp(arg, "serial", 6)) {
54 port = DEFAULT_SERIAL_PORT;
63 * "serial,0x3f8,115200"
64 * "serial,ttyS0,115200"
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;
73 } else if (!strncmp(arg + pos, "ttyS", 4)) {
74 static const int bases[] = { 0x3f8, 0x2f8 };
77 if (!strncmp(arg + pos, "ttyS", 4))
80 if (arg[pos++] == '1')
89 baud = simple_strtoull(arg + pos, &e, 0);
90 if (baud == 0 || arg + pos == e)
95 early_serial_init(port, baud);
98 #define BASE_BAUD (1843200/16)
99 static unsigned int probe_baud(int port)
101 unsigned char lcr, dll, dlh;
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;
111 return BASE_BAUD / quot;
114 static void parse_console_uart8250(void)
116 char optstr[64], *options;
117 int baud = DEFAULT_BAUD;
121 * console=uart8250,io,0x3f8,115200n8
122 * need to make sure it is last one console !
124 if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
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);
136 if (options && (options[0] == ','))
137 baud = simple_strtoull(options + 1, &options, 0);
139 baud = probe_baud(port);
142 early_serial_init(port, baud);
145 void console_init(void)
149 if (!early_serial_base)
150 parse_console_uart8250();