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
26static 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
46static 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)
102static 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
117static 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
148void console_init(void)
149{
150	parse_earlyprintk();
151
152	if (!early_serial_base)
153		parse_console_uart8250();
154}
155