1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright 2007 rPath, Inc. - All Rights Reserved
5 * Copyright 2009 Intel Corporation; author H. Peter Anvin
7 * This file is part of the Linux kernel, and is made available under
8 * the terms of the GNU General Public License version 2.
10 * ----------------------------------------------------------------------- */
13 * Very simple screen and serial I/O
18 #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
20 static int early_serial_base
;
26 #define TXR 0 /* Transmit register (WRITE) */
27 #define RXR 0 /* Receive register (READ) */
28 #define IER 1 /* Interrupt Enable */
29 #define IIR 2 /* Interrupt ID */
30 #define FCR 2 /* FIFO control */
31 #define LCR 3 /* Line control */
32 #define MCR 4 /* Modem control */
33 #define LSR 5 /* Line Status */
34 #define MSR 6 /* Modem Status */
35 #define DLL 0 /* Divisor Latch Low */
36 #define DLH 1 /* Divisor latch High */
38 #define DEFAULT_BAUD 9600
41 * These functions are in .inittext so they can be used to signal
42 * error during initialization.
45 static void __attribute__((section(".inittext"))) serial_putchar(int ch
)
47 unsigned timeout
= 0xffff;
49 while ((inb(early_serial_base
+ LSR
) & XMTRDY
) == 0 && --timeout
)
52 outb(ch
, early_serial_base
+ TXR
);
55 static void __attribute__((section(".inittext"))) bios_putchar(int ch
)
64 intcall(0x10, &ireg
, NULL
);
67 void __attribute__((section(".inittext"))) putchar(int ch
)
70 putchar('\r'); /* \n -> \r\n */
74 if (early_serial_base
!= 0)
78 void __attribute__((section(".inittext"))) puts(const char *str
)
85 * Read the CMOS clock through the BIOS, and return the
89 static u8
gettime(void)
91 struct biosregs ireg
, oreg
;
95 intcall(0x1a, &ireg
, &oreg
);
101 * Read from the keyboard
105 struct biosregs ireg
, oreg
;
108 /* ireg.ah = 0x00; */
109 intcall(0x16, &ireg
, &oreg
);
114 static int kbd_pending(void)
116 struct biosregs ireg
, oreg
;
120 intcall(0x16, &ireg
, &oreg
);
122 return !(oreg
.eflags
& X86_EFLAGS_ZF
);
134 int getchar_timeout(void)
152 return 0; /* Timeout! */
155 static void early_serial_init(int port
, int baud
)
160 outb(0x3, port
+ LCR
); /* 8n1 */
161 outb(0, port
+ IER
); /* no interrupt */
162 outb(0, port
+ FCR
); /* no fifo */
163 outb(0x3, port
+ MCR
); /* DTR + RTS */
165 divisor
= 115200 / baud
;
167 outb(c
| DLAB
, port
+ LCR
);
168 outb(divisor
& 0xff, port
+ DLL
);
169 outb((divisor
>> 8) & 0xff, port
+ DLH
);
170 outb(c
& ~DLAB
, port
+ LCR
);
172 early_serial_base
= port
;
174 printf("Early serial console at I/O port 0x%x baud: %d\n", port
, baud
);
177 static void parse_earlyprintk(void)
179 int baud
= DEFAULT_BAUD
;
184 if (cmdline_find_option("earlyprintk", arg
, sizeof arg
) > 0) {
187 if (!strncmp(arg
, "serial", 6)) {
188 port
= DEFAULT_SERIAL_PORT
;
195 if (!strncmp(arg
, "ttyS", 4)) {
196 static const int bases
[] = { 0x3f8, 0x2f8 };
199 if (!strncmp(arg
+ pos
, "ttyS", 4))
202 if (arg
[pos
++] == '1')
211 baud
= simple_strtoull(arg
+ pos
, &e
, 0);
212 if (baud
== 0 || arg
+ pos
== e
)
217 early_serial_init(port
, baud
);
220 #define BASE_BAUD (1843200/16)
221 static unsigned int probe_baud(int port
)
223 unsigned char lcr
, dll
, dlh
;
226 lcr
= inb(port
+ LCR
);
227 outb(lcr
| DLAB
, port
+ LCR
);
228 dll
= inb(port
+ DLL
);
229 dlh
= inb(port
+ DLH
);
230 outb(lcr
, port
+ LCR
);
231 quot
= (dlh
<< 8) | dll
;
233 return BASE_BAUD
/ quot
;
236 static void parse_console_uart8250(void)
238 char optstr
[64], *options
;
239 int baud
= DEFAULT_BAUD
;
243 * console=uart8250,io,0x3f8,115200n8
244 * need to make sure it is last one console !
246 if (cmdline_find_option("console", optstr
, sizeof optstr
) <= 0)
251 if (!strncmp(options
, "uart8250,io,", 12))
252 port
= simple_strtoull(options
+ 12, &options
, 0);
253 else if (!strncmp(options
, "uart,io,", 8))
254 port
= simple_strtoull(options
+ 8, &options
, 0);
258 if (options
&& (options
[0] == ','))
259 baud
= simple_strtoull(options
+ 1, &options
, 0);
261 baud
= probe_baud(port
);
264 early_serial_init(port
, baud
);
267 void console_init(void)
271 if (!early_serial_base
)
272 parse_console_uart8250();