tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Early serial console for 8250/16550 devices
3 *
4 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
5 * Bjorn Helgaas <bjorn.helgaas@hp.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
12 * and on early_printk.c by Andi Kleen.
13 *
14 * This is for use before the serial driver has initialized, in
15 * particular, before the UARTs have been discovered and named.
16 * Instead of specifying the console device as, e.g., "ttyS0",
17 * we locate the device directly by its MMIO or I/O port address.
18 *
19 * The user can specify the device directly, e.g.,
20 * console=uart,io,0x3f8,9600n8
21 * console=uart,mmio,0xff5e0000,115200n8
22 * or platform code can call early_uart_console_init() to set
23 * the early UART device.
24 *
25 * After the normal serial driver starts, we try to locate the
26 * matching ttyS device and start a console there.
27 */
28
29#include <linux/tty.h>
30#include <linux/init.h>
31#include <linux/console.h>
32#include <linux/serial_core.h>
33#include <linux/serial_reg.h>
34#include <linux/serial.h>
35#include <asm/io.h>
36#include <asm/serial.h>
37
38struct early_uart_device {
39 struct uart_port port;
40 char options[16]; /* e.g., 115200n8 */
41 unsigned int baud;
42};
43
44static struct early_uart_device early_device __initdata;
45static int early_uart_registered __initdata;
46
47static unsigned int __init serial_in(struct uart_port *port, int offset)
48{
49 if (port->iotype == UPIO_MEM)
50 return readb(port->membase + offset);
51 else
52 return inb(port->iobase + offset);
53}
54
55static void __init serial_out(struct uart_port *port, int offset, int value)
56{
57 if (port->iotype == UPIO_MEM)
58 writeb(value, port->membase + offset);
59 else
60 outb(value, port->iobase + offset);
61}
62
63#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
64
65static void __init wait_for_xmitr(struct uart_port *port)
66{
67 unsigned int status;
68
69 for (;;) {
70 status = serial_in(port, UART_LSR);
71 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
72 return;
73 cpu_relax();
74 }
75}
76
77static void __init putc(struct uart_port *port, unsigned char c)
78{
79 wait_for_xmitr(port);
80 serial_out(port, UART_TX, c);
81}
82
83static void __init early_uart_write(struct console *console, const char *s, unsigned int count)
84{
85 struct uart_port *port = &early_device.port;
86 unsigned int ier;
87
88 /* Save the IER and disable interrupts */
89 ier = serial_in(port, UART_IER);
90 serial_out(port, UART_IER, 0);
91
92 while (*s && count-- > 0) {
93 putc(port, *s);
94 if (*s == '\n')
95 putc(port, '\r');
96 s++;
97 }
98
99 /* Wait for transmitter to become empty and restore the IER */
100 wait_for_xmitr(port);
101 serial_out(port, UART_IER, ier);
102}
103
104static unsigned int __init probe_baud(struct uart_port *port)
105{
106 unsigned char lcr, dll, dlm;
107 unsigned int quot;
108
109 lcr = serial_in(port, UART_LCR);
110 serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
111 dll = serial_in(port, UART_DLL);
112 dlm = serial_in(port, UART_DLM);
113 serial_out(port, UART_LCR, lcr);
114
115 quot = (dlm << 8) | dll;
116 return (port->uartclk / 16) / quot;
117}
118
119static void __init init_port(struct early_uart_device *device)
120{
121 struct uart_port *port = &device->port;
122 unsigned int divisor;
123 unsigned char c;
124
125 serial_out(port, UART_LCR, 0x3); /* 8n1 */
126 serial_out(port, UART_IER, 0); /* no interrupt */
127 serial_out(port, UART_FCR, 0); /* no fifo */
128 serial_out(port, UART_MCR, 0x3); /* DTR + RTS */
129
130 divisor = port->uartclk / (16 * device->baud);
131 c = serial_in(port, UART_LCR);
132 serial_out(port, UART_LCR, c | UART_LCR_DLAB);
133 serial_out(port, UART_DLL, divisor & 0xff);
134 serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
135 serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
136}
137
138static int __init parse_options(struct early_uart_device *device, char *options)
139{
140 struct uart_port *port = &device->port;
141 int mapsize = 64;
142 int mmio, length;
143
144 if (!options)
145 return -ENODEV;
146
147 port->uartclk = BASE_BAUD * 16;
148 if (!strncmp(options, "mmio,", 5)) {
149 port->iotype = UPIO_MEM;
150 port->mapbase = simple_strtoul(options + 5, &options, 0);
151 port->membase = ioremap(port->mapbase, mapsize);
152 if (!port->membase) {
153 printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n",
154 __FUNCTION__, port->mapbase);
155 return -ENOMEM;
156 }
157 mmio = 1;
158 } else if (!strncmp(options, "io,", 3)) {
159 port->iotype = UPIO_PORT;
160 port->iobase = simple_strtoul(options + 3, &options, 0);
161 mmio = 0;
162 } else
163 return -EINVAL;
164
165 if ((options = strchr(options, ','))) {
166 options++;
167 device->baud = simple_strtoul(options, NULL, 0);
168 length = min(strcspn(options, " "), sizeof(device->options));
169 strncpy(device->options, options, length);
170 } else {
171 device->baud = probe_baud(port);
172 snprintf(device->options, sizeof(device->options), "%u",
173 device->baud);
174 }
175
176 printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n",
177 mmio ? "MMIO" : "I/O port",
178 mmio ? port->mapbase : (unsigned long) port->iobase,
179 device->options);
180 return 0;
181}
182
183static int __init early_uart_setup(struct console *console, char *options)
184{
185 struct early_uart_device *device = &early_device;
186 int err;
187
188 if (device->port.membase || device->port.iobase)
189 return 0;
190
191 if ((err = parse_options(device, options)) < 0)
192 return err;
193
194 init_port(device);
195 return 0;
196}
197
198static struct console early_uart_console __initdata = {
199 .name = "uart",
200 .write = early_uart_write,
201 .setup = early_uart_setup,
202 .flags = CON_PRINTBUFFER,
203 .index = -1,
204};
205
206static int __init early_uart_console_init(void)
207{
208 if (!early_uart_registered) {
209 register_console(&early_uart_console);
210 early_uart_registered = 1;
211 }
212 return 0;
213}
214console_initcall(early_uart_console_init);
215
216int __init early_serial_console_init(char *cmdline)
217{
218 char *options;
219 int err;
220
221 options = strstr(cmdline, "console=uart,");
222 if (!options)
223 return -ENODEV;
224
225 options = strchr(cmdline, ',') + 1;
226 if ((err = early_uart_setup(NULL, options)) < 0)
227 return err;
228 return early_uart_console_init();
229}
230
231static int __init early_uart_console_switch(void)
232{
233 struct early_uart_device *device = &early_device;
234 struct uart_port *port = &device->port;
235 int mmio, line;
236
237 if (!(early_uart_console.flags & CON_ENABLED))
238 return 0;
239
240 /* Try to start the normal driver on a matching line. */
241 mmio = (port->iotype == UPIO_MEM);
242 line = serial8250_start_console(port, device->options);
243 if (line < 0)
244 printk("No ttyS device at %s 0x%lx for console\n",
245 mmio ? "MMIO" : "I/O port",
246 mmio ? port->mapbase :
247 (unsigned long) port->iobase);
248
249 unregister_console(&early_uart_console);
250 if (mmio)
251 iounmap(port->membase);
252
253 return 0;
254}
255late_initcall(early_uart_console_switch);