summaryrefslogtreecommitdiffstats
path: root/drivers/serial/8250_early.c
blob: 7e511199b4c5c91f09fcde69ced030c7ca15043d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
/*
 * Early serial console for 8250/16550 devices
 *
 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
 *	Bjorn Helgaas <bjorn.helgaas@hp.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
 * and on early_printk.c by Andi Kleen.
 *
 * This is for use before the serial driver has initialized, in
 * particular, before the UARTs have been discovered and named.
 * Instead of specifying the console device as, e.g., "ttyS0",
 * we locate the device directly by its MMIO or I/O port address.
 *
 * The user can specify the device directly, e.g.,
 *	console=uart,io,0x3f8,9600n8
 *	console=uart,mmio,0xff5e0000,115200n8
 * or platform code can call early_uart_console_init() to set
 * the early UART device.
 *
 * After the normal serial driver starts, we try to locate the
 * matching ttyS device and start a console there.
 */

#include <linux/tty.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/serial_core.h>
#include <linux/serial_reg.h>
#include <linux/serial.h>
#include <asm/io.h>
#include <asm/serial.h>

struct early_uart_device {
	struct uart_port port;
	char options[16];		/* e.g., 115200n8 */
	unsigned int baud;
};

static struct early_uart_device early_device __initdata;
static int early_uart_registered __initdata;

static unsigned int __init serial_in(struct uart_port *port, int offset)
{
	if (port->iotype == UPIO_MEM)
		return readb(port->membase + offset);
	else
		return inb(port->iobase + offset);
}

static void __init serial_out(struct uart_port *port, int offset, int value)
{
	if (port->iotype == UPIO_MEM)
		writeb(value, port->membase + offset);
	else
		outb(value, port->iobase + offset);
}

#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

static void __init wait_for_xmitr(struct uart_port *port)
{
	unsigned int status;

	for (;;) {
		status = serial_in(port, UART_LSR);
		if ((status & BOTH_EMPTY) == BOTH_EMPTY)
			return;
		cpu_relax();
	}
}

static void __init putc(struct uart_port *port, int c)
{
	wait_for_xmitr(port);
	serial_out(port, UART_TX, c);
}

static void __init early_uart_write(struct console *console, const char *s, unsigned int count)
{
	struct uart_port *port = &early_device.port;
	unsigned int ier;

	/* Save the IER and disable interrupts */
	ier = serial_in(port, UART_IER);
	serial_out(port, UART_IER, 0);

	uart_console_write(port, s, count, putc);

	/* Wait for transmitter to become empty and restore the IER */
	wait_for_xmitr(port);
	serial_out(port, UART_IER, ier);
}

static unsigned int __init probe_baud(struct uart_port *port)
{
	unsigned char lcr, dll, dlm;
	unsigned int quot;

	lcr = serial_in(port, UART_LCR);
	serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
	dll = serial_in(port, UART_DLL);
	dlm = serial_in(port, UART_DLM);
	serial_out(port, UART_LCR, lcr);

	quot = (dlm << 8) | dll;
	return (port->uartclk / 16) / quot;
}

static void __init init_port(struct early_uart_device *device)
{
	struct uart_port *port = &device->port;
	unsigned int divisor;
	unsigned char c;

	serial_out(port, UART_LCR, 0x3);	/* 8n1 */
	serial_out(port, UART_IER, 0);		/* no interrupt */
	serial_out(port, UART_FCR, 0);		/* no fifo */
	serial_out(port, UART_MCR, 0x3);	/* DTR + RTS */

	divisor = port->uartclk / (16 * device->baud);
	c = serial_in(port, UART_LCR);
	serial_out(port, UART_LCR, c | UART_LCR_DLAB);
	serial_out(port, UART_DLL, divisor & 0xff);
	serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
	serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
}

static int __init parse_options(struct early_uart_device *device, char *options)
{
	struct uart_port *port = &device->port;
	int mapsize = 64;
	int mmio, length;

	if (!options)
		return -ENODEV;

	port->uartclk = BASE_BAUD * 16;
	if (!strncmp(options, "mmio,", 5)) {
		port->iotype = UPIO_MEM;
		port->mapbase = simple_strtoul(options + 5, &options, 0);
		port->membase = ioremap(port->mapbase, mapsize);
		if (!port->membase) {
			printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n",
				__FUNCTION__, port->mapbase);
			return -ENOMEM;
		}
		mmio = 1;
	} else if (!strncmp(options, "io,", 3)) {
		port->iotype = UPIO_PORT;
		port->iobase = simple_strtoul(options + 3, &options, 0);
		mmio = 0;
	} else
		return -EINVAL;

	if ((options = strchr(options, ','))) {
		options++;
		device->baud = simple_strtoul(options, NULL, 0);
		length = min(strcspn(options, " "), sizeof(device->options));
		strncpy(device->options, options, length);
	} else {
		device->baud = probe_baud(port);
		snprintf(device->options, sizeof(device->options), "%u",
			device->baud);
	}

	printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n",
		mmio ? "MMIO" : "I/O port",
		mmio ? port->mapbase : (unsigned long) port->iobase,
		device->options);
	return 0;
}

static int __init early_uart_setup(struct console *console, char *options)
{
	struct early_uart_device *device = &early_device;
	int err;

	if (device->port.membase || device->port.iobase)
		return 0;

	if ((err = parse_options(device, options)) < 0)
		return err;

	init_port(device);
	return 0;
}

static struct console early_uart_console __initdata = {
	.name	= "uart",
	.write	= early_uart_write,
	.setup	= early_uart_setup,
	.flags	= CON_PRINTBUFFER,
	.index	= -1,
};

static int __init early_uart_console_init(void)
{
	if (!early_uart_registered) {
		register_console(&early_uart_console);
		early_uart_registered = 1;
	}
	return 0;
}
console_initcall(early_uart_console_init);

int __init early_serial_console_init(char *cmdline)
{
	char *options;
	int err;

	options = strstr(cmdline, "console=uart,");
	if (!options)
		return -ENODEV;

	options = strchr(cmdline, ',') + 1;
	if ((err = early_uart_setup(NULL, options)) < 0)
		return err;
	return early_uart_console_init();
}

static int __init early_uart_console_switch(void)
{
	struct early_uart_device *device = &early_device;
	struct uart_port *port = &device->port;
	int mmio, line;

	if (!(early_uart_console.flags & CON_ENABLED))
		return 0;

	/* Try to start the normal driver on a matching line.  */
	mmio = (port->iotype == UPIO_MEM);
	line = serial8250_start_console(port, device->options);
	if (line < 0)
		printk("No ttyS device at %s 0x%lx for console\n",
			mmio ? "MMIO" : "I/O port",
			mmio ? port->mapbase :
			    (unsigned long) port->iobase);

	unregister_console(&early_uart_console);
	if (mmio)
		iounmap(port->membase);

	return 0;
}
late_initcall(early_uart_console_switch);