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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
cb18ef0d KC |
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 | */ | |
f4ed2877 YL |
6 | #include "boot.h" |
7 | ||
8 | #define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */ | |
9 | ||
f4ed2877 YL |
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("earlyprintk", arg, 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 | ||
74b3c444 YL |
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)) { | |
f4ed2877 YL |
77 | static const int bases[] = { 0x3f8, 0x2f8 }; |
78 | int idx = 0; | |
79 | ||
b3463001 AK |
80 | /* += strlen("ttyS"); */ |
81 | pos += 4; | |
f4ed2877 YL |
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("console", optstr, 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 | } |