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
early_serial_init(int port,int baud)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
parse_earlyprintk(void)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
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)
probe_baud(int port)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
parse_console_uart8250(void)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
console_init(void)148 void console_init(void)
149 {
150 parse_earlyprintk();
151
152 if (!early_serial_base)
153 parse_console_uart8250();
154 }
155
