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, int 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 uart_console_write(port, s, count, putc);
93
94 /* Wait for transmitter to become empty and restore the IER */
95 wait_for_xmitr(port);
96 serial_out(port, UART_IER, ier);
97}
98
99static unsigned int __init probe_baud(struct uart_port *port)
100{
101 unsigned char lcr, dll, dlm;
102 unsigned int quot;
103
104 lcr = serial_in(port, UART_LCR);
105 serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
106 dll = serial_in(port, UART_DLL);
107 dlm = serial_in(port, UART_DLM);
108 serial_out(port, UART_LCR, lcr);
109
110 quot = (dlm << 8) | dll;
111 return (port->uartclk / 16) / quot;
112}
113
114static void __init init_port(struct early_uart_device *device)
115{
116 struct uart_port *port = &device->port;
117 unsigned int divisor;
118 unsigned char c;
119
120 serial_out(port, UART_LCR, 0x3); /* 8n1 */
121 serial_out(port, UART_IER, 0); /* no interrupt */
122 serial_out(port, UART_FCR, 0); /* no fifo */
123 serial_out(port, UART_MCR, 0x3); /* DTR + RTS */
124
125 divisor = port->uartclk / (16 * device->baud);
126 c = serial_in(port, UART_LCR);
127 serial_out(port, UART_LCR, c | UART_LCR_DLAB);
128 serial_out(port, UART_DLL, divisor & 0xff);
129 serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
130 serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
131}
132
133static int __init parse_options(struct early_uart_device *device, char *options)
134{
135 struct uart_port *port = &device->port;
136 int mapsize = 64;
137 int mmio, length;
138
139 if (!options)
140 return -ENODEV;
141
142 port->uartclk = BASE_BAUD * 16;
143 if (!strncmp(options, "mmio,", 5)) {
144 port->iotype = UPIO_MEM;
145 port->mapbase = simple_strtoul(options + 5, &options, 0);
146 port->membase = ioremap(port->mapbase, mapsize);
147 if (!port->membase) {
148 printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n",
149 __FUNCTION__, port->mapbase);
150 return -ENOMEM;
151 }
152 mmio = 1;
153 } else if (!strncmp(options, "io,", 3)) {
154 port->iotype = UPIO_PORT;
155 port->iobase = simple_strtoul(options + 3, &options, 0);
156 mmio = 0;
157 } else
158 return -EINVAL;
159
160 if ((options = strchr(options, ','))) {
161 options++;
162 device->baud = simple_strtoul(options, NULL, 0);
163 length = min(strcspn(options, " "), sizeof(device->options));
164 strncpy(device->options, options, length);
165 } else {
166 device->baud = probe_baud(port);
167 snprintf(device->options, sizeof(device->options), "%u",
168 device->baud);
169 }
170
171 printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n",
172 mmio ? "MMIO" : "I/O port",
173 mmio ? port->mapbase : (unsigned long) port->iobase,
174 device->options);
175 return 0;
176}
177
178static int __init early_uart_setup(struct console *console, char *options)
179{
180 struct early_uart_device *device = &early_device;
181 int err;
182
183 if (device->port.membase || device->port.iobase)
184 return 0;
185
186 if ((err = parse_options(device, options)) < 0)
187 return err;
188
189 init_port(device);
190 return 0;
191}
192
193static struct console early_uart_console __initdata = {
194 .name = "uart",
195 .write = early_uart_write,
196 .setup = early_uart_setup,
197 .flags = CON_PRINTBUFFER,
198 .index = -1,
199};
200
201static int __init early_uart_console_init(void)
202{
203 if (!early_uart_registered) {
204 register_console(&early_uart_console);
205 early_uart_registered = 1;
206 }
207 return 0;
208}
209console_initcall(early_uart_console_init);
210
211int __init early_serial_console_init(char *cmdline)
212{
213 char *options;
214 int err;
215
216 options = strstr(cmdline, "console=uart,");
217 if (!options)
218 return -ENODEV;
219
220 options = strchr(cmdline, ',') + 1;
221 if ((err = early_uart_setup(NULL, options)) < 0)
222 return err;
223 return early_uart_console_init();
224}
225
226static int __init early_uart_console_switch(void)
227{
228 struct early_uart_device *device = &early_device;
229 struct uart_port *port = &device->port;
230 int mmio, line;
231
232 if (!(early_uart_console.flags & CON_ENABLED))
233 return 0;
234
235 /* Try to start the normal driver on a matching line. */
236 mmio = (port->iotype == UPIO_MEM);
237 line = serial8250_start_console(port, device->options);
238 if (line < 0)
239 printk("No ttyS device at %s 0x%lx for console\n",
240 mmio ? "MMIO" : "I/O port",
241 mmio ? port->mapbase :
242 (unsigned long) port->iobase);
243
244 unregister_console(&early_uart_console);
245 if (mmio)
246 iounmap(port->membase);
247
248 return 0;
249}
250late_initcall(early_uart_console_switch);