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();
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