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1da177e4 LT |
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 | ||
38 | struct early_uart_device { | |
39 | struct uart_port port; | |
40 | char options[16]; /* e.g., 115200n8 */ | |
41 | unsigned int baud; | |
42 | }; | |
43 | ||
44 | static struct early_uart_device early_device __initdata; | |
45 | static int early_uart_registered __initdata; | |
46 | ||
47 | static 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 | ||
55 | static 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 | ||
65 | static 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 | ||
77 | static 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 | ||
83 | static 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 | ||
104 | static 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 | ||
119 | static 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 | ||
138 | static 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, 0, 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 | ||
183 | static 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 | ||
198 | static 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 | ||
206 | static 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 | } | |
214 | console_initcall(early_uart_console_init); | |
215 | ||
216 | int __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 | ||
231 | static 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 | } | |
255 | late_initcall(early_uart_console_switch); |