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;
61 if (!strncmp(arg, "ttyS", 4)) {
62 static const int bases[] = { 0x3f8, 0x2f8 };
65 if (!strncmp(arg + pos, "ttyS", 4))
68 if (arg[pos++] == '1')
77 baud = simple_strtoull(arg + pos, &e, 0);
78 if (baud == 0 || arg + pos == e)
83 early_serial_init(port, baud);
86 #define BASE_BAUD (1843200/16)
87 static unsigned int probe_baud(int port)
89 unsigned char lcr, dll, dlh;
92 lcr = inb(port + LCR);
93 outb(lcr | DLAB, port + LCR);
94 dll = inb(port + DLL);
95 dlh = inb(port + DLH);
96 outb(lcr, port + LCR);
97 quot = (dlh << 8) | dll;
99 return BASE_BAUD / quot;
102 static void parse_console_uart8250(void)
104 char optstr[64], *options;
105 int baud = DEFAULT_BAUD;
109 * console=uart8250,io,0x3f8,115200n8
110 * need to make sure it is last one console !
112 if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
117 if (!strncmp(options, "uart8250,io,", 12))
118 port = simple_strtoull(options + 12, &options, 0);
119 else if (!strncmp(options, "uart,io,", 8))
120 port = simple_strtoull(options + 8, &options, 0);
124 if (options && (options[0] == ','))
125 baud = simple_strtoull(options + 1, &options, 0);
127 baud = probe_baud(port);
130 early_serial_init(port, baud);
133 void console_init(void)
137 if (!early_serial_base)
138 parse_console_uart8250();