1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Serial port routines for use during early boot reporting. This code is |
4 | * included from both the compressed kernel and the regular kernel. |
5 | */ |
6 | #include "boot.h" |
7 | |
8 | #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */ |
9 | |
10 | #define DLAB 0x80 |
11 | |
12 | #define TXR 0 /* Transmit register (WRITE) */ |
13 | #define RXR 0 /* Receive register (READ) */ |
14 | #define IER 1 /* Interrupt Enable */ |
15 | #define IIR 2 /* Interrupt ID */ |
16 | #define FCR 2 /* FIFO control */ |
17 | #define LCR 3 /* Line control */ |
18 | #define MCR 4 /* Modem control */ |
19 | #define LSR 5 /* Line Status */ |
20 | #define MSR 6 /* Modem Status */ |
21 | #define DLL 0 /* Divisor Latch Low */ |
22 | #define DLH 1 /* Divisor latch High */ |
23 | |
24 | #define DEFAULT_BAUD 9600 |
25 | |
26 | static void early_serial_init(int port, int baud) |
27 | { |
28 | unsigned char c; |
29 | unsigned divisor; |
30 | |
31 | outb(0x3, port + LCR); /* 8n1 */ |
32 | outb(0, port + IER); /* no interrupt */ |
33 | outb(0, port + FCR); /* no fifo */ |
34 | outb(0x3, port + MCR); /* DTR + RTS */ |
35 | |
36 | divisor = 115200 / baud; |
37 | c = inb(port + LCR); |
38 | outb(c | DLAB, port + LCR); |
39 | outb(divisor & 0xff, port + DLL); |
40 | outb((divisor >> 8) & 0xff, port + DLH); |
41 | outb(c & ~DLAB, port + LCR); |
42 | |
43 | early_serial_base = port; |
44 | } |
45 | |
46 | static void parse_earlyprintk(void) |
47 | { |
48 | int baud = DEFAULT_BAUD; |
49 | char arg[32]; |
50 | int pos = 0; |
51 | int port = 0; |
52 | |
53 | if (cmdline_find_option(option: "earlyprintk" , buffer: arg, bufsize: sizeof(arg)) > 0) { |
54 | char *e; |
55 | |
56 | if (!strncmp(arg, "serial" , 6)) { |
57 | port = DEFAULT_SERIAL_PORT; |
58 | pos += 6; |
59 | } |
60 | |
61 | if (arg[pos] == ',') |
62 | pos++; |
63 | |
64 | /* |
65 | * make sure we have |
66 | * "serial,0x3f8,115200" |
67 | * "serial,ttyS0,115200" |
68 | * "ttyS0,115200" |
69 | */ |
70 | if (pos == 7 && !strncmp(arg + pos, "0x" , 2)) { |
71 | port = simple_strtoull(arg + pos, &e, 16); |
72 | if (port == 0 || arg + pos == e) |
73 | port = DEFAULT_SERIAL_PORT; |
74 | else |
75 | pos = e - arg; |
76 | } else if (!strncmp(arg + pos, "ttyS" , 4)) { |
77 | static const int bases[] = { 0x3f8, 0x2f8 }; |
78 | int idx = 0; |
79 | |
80 | /* += strlen("ttyS"); */ |
81 | pos += 4; |
82 | |
83 | if (arg[pos++] == '1') |
84 | idx = 1; |
85 | |
86 | port = bases[idx]; |
87 | } |
88 | |
89 | if (arg[pos] == ',') |
90 | pos++; |
91 | |
92 | baud = simple_strtoull(arg + pos, &e, 0); |
93 | if (baud == 0 || arg + pos == e) |
94 | baud = DEFAULT_BAUD; |
95 | } |
96 | |
97 | if (port) |
98 | early_serial_init(port, baud); |
99 | } |
100 | |
101 | #define BASE_BAUD (1843200/16) |
102 | static unsigned int probe_baud(int port) |
103 | { |
104 | unsigned char lcr, dll, dlh; |
105 | unsigned int quot; |
106 | |
107 | lcr = inb(port + LCR); |
108 | outb(lcr | DLAB, port + LCR); |
109 | dll = inb(port + DLL); |
110 | dlh = inb(port + DLH); |
111 | outb(lcr, port + LCR); |
112 | quot = (dlh << 8) | dll; |
113 | |
114 | return BASE_BAUD / quot; |
115 | } |
116 | |
117 | static void parse_console_uart8250(void) |
118 | { |
119 | char optstr[64], *options; |
120 | int baud = DEFAULT_BAUD; |
121 | int port = 0; |
122 | |
123 | /* |
124 | * console=uart8250,io,0x3f8,115200n8 |
125 | * need to make sure it is last one console ! |
126 | */ |
127 | if (cmdline_find_option(option: "console" , buffer: optstr, bufsize: sizeof(optstr)) <= 0) |
128 | return; |
129 | |
130 | options = optstr; |
131 | |
132 | if (!strncmp(options, "uart8250,io," , 12)) |
133 | port = simple_strtoull(options + 12, &options, 0); |
134 | else if (!strncmp(options, "uart,io," , 8)) |
135 | port = simple_strtoull(options + 8, &options, 0); |
136 | else |
137 | return; |
138 | |
139 | if (options && (options[0] == ',')) |
140 | baud = simple_strtoull(options + 1, &options, 0); |
141 | else |
142 | baud = probe_baud(port); |
143 | |
144 | if (port) |
145 | early_serial_init(port, baud); |
146 | } |
147 | |
148 | void console_init(void) |
149 | { |
150 | parse_earlyprintk(); |
151 | |
152 | if (!early_serial_base) |
153 | parse_console_uart8250(); |
154 | } |
155 | |