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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., | |
18a8bd94 YL |
20 | * earlycon=uart8250,io,0x3f8,9600n8 |
21 | * earlycon=uart8250,mmio,0xff5e0000,115200n8 | |
22 | * or | |
23 | * console=uart8250,io,0x3f8,9600n8 | |
24 | * console=uart8250,mmio,0xff5e0000,115200n8 | |
1da177e4 LT |
25 | */ |
26 | ||
27 | #include <linux/tty.h> | |
28 | #include <linux/init.h> | |
29 | #include <linux/console.h> | |
30 | #include <linux/serial_core.h> | |
31 | #include <linux/serial_reg.h> | |
32 | #include <linux/serial.h> | |
18a8bd94 | 33 | #include <linux/serial_8250.h> |
1da177e4 LT |
34 | #include <asm/io.h> |
35 | #include <asm/serial.h> | |
18a8bd94 YL |
36 | #ifdef CONFIG_FIX_EARLYCON_MEM |
37 | #include <asm/pgtable.h> | |
38 | #include <asm/fixmap.h> | |
39 | #endif | |
1da177e4 | 40 | |
18a8bd94 | 41 | struct early_serial8250_device { |
1da177e4 LT |
42 | struct uart_port port; |
43 | char options[16]; /* e.g., 115200n8 */ | |
44 | unsigned int baud; | |
45 | }; | |
46 | ||
18a8bd94 | 47 | static struct early_serial8250_device early_device; |
1da177e4 LT |
48 | |
49 | static unsigned int __init serial_in(struct uart_port *port, int offset) | |
50 | { | |
51 | if (port->iotype == UPIO_MEM) | |
52 | return readb(port->membase + offset); | |
53 | else | |
54 | return inb(port->iobase + offset); | |
55 | } | |
56 | ||
57 | static void __init serial_out(struct uart_port *port, int offset, int value) | |
58 | { | |
59 | if (port->iotype == UPIO_MEM) | |
60 | writeb(value, port->membase + offset); | |
61 | else | |
62 | outb(value, port->iobase + offset); | |
63 | } | |
64 | ||
65 | #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) | |
66 | ||
67 | static void __init wait_for_xmitr(struct uart_port *port) | |
68 | { | |
69 | unsigned int status; | |
70 | ||
71 | for (;;) { | |
72 | status = serial_in(port, UART_LSR); | |
73 | if ((status & BOTH_EMPTY) == BOTH_EMPTY) | |
74 | return; | |
75 | cpu_relax(); | |
76 | } | |
77 | } | |
78 | ||
d358788f | 79 | static void __init putc(struct uart_port *port, int c) |
1da177e4 LT |
80 | { |
81 | wait_for_xmitr(port); | |
82 | serial_out(port, UART_TX, c); | |
83 | } | |
84 | ||
18a8bd94 | 85 | static void __init early_serial8250_write(struct console *console, const char *s, unsigned int count) |
1da177e4 LT |
86 | { |
87 | struct uart_port *port = &early_device.port; | |
88 | unsigned int ier; | |
89 | ||
90 | /* Save the IER and disable interrupts */ | |
91 | ier = serial_in(port, UART_IER); | |
92 | serial_out(port, UART_IER, 0); | |
93 | ||
d358788f | 94 | uart_console_write(port, s, count, putc); |
1da177e4 LT |
95 | |
96 | /* Wait for transmitter to become empty and restore the IER */ | |
97 | wait_for_xmitr(port); | |
98 | serial_out(port, UART_IER, ier); | |
99 | } | |
100 | ||
101 | static unsigned int __init probe_baud(struct uart_port *port) | |
102 | { | |
103 | unsigned char lcr, dll, dlm; | |
104 | unsigned int quot; | |
105 | ||
106 | lcr = serial_in(port, UART_LCR); | |
107 | serial_out(port, UART_LCR, lcr | UART_LCR_DLAB); | |
108 | dll = serial_in(port, UART_DLL); | |
109 | dlm = serial_in(port, UART_DLM); | |
110 | serial_out(port, UART_LCR, lcr); | |
111 | ||
112 | quot = (dlm << 8) | dll; | |
113 | return (port->uartclk / 16) / quot; | |
114 | } | |
115 | ||
18a8bd94 | 116 | static void __init init_port(struct early_serial8250_device *device) |
1da177e4 LT |
117 | { |
118 | struct uart_port *port = &device->port; | |
119 | unsigned int divisor; | |
120 | unsigned char c; | |
121 | ||
122 | serial_out(port, UART_LCR, 0x3); /* 8n1 */ | |
123 | serial_out(port, UART_IER, 0); /* no interrupt */ | |
124 | serial_out(port, UART_FCR, 0); /* no fifo */ | |
125 | serial_out(port, UART_MCR, 0x3); /* DTR + RTS */ | |
126 | ||
127 | divisor = port->uartclk / (16 * device->baud); | |
128 | c = serial_in(port, UART_LCR); | |
129 | serial_out(port, UART_LCR, c | UART_LCR_DLAB); | |
130 | serial_out(port, UART_DLL, divisor & 0xff); | |
131 | serial_out(port, UART_DLM, (divisor >> 8) & 0xff); | |
132 | serial_out(port, UART_LCR, c & ~UART_LCR_DLAB); | |
133 | } | |
134 | ||
18a8bd94 | 135 | static int __init parse_options(struct early_serial8250_device *device, char *options) |
1da177e4 LT |
136 | { |
137 | struct uart_port *port = &device->port; | |
1da177e4 LT |
138 | int mmio, length; |
139 | ||
140 | if (!options) | |
141 | return -ENODEV; | |
142 | ||
143 | port->uartclk = BASE_BAUD * 16; | |
144 | if (!strncmp(options, "mmio,", 5)) { | |
145 | port->iotype = UPIO_MEM; | |
146 | port->mapbase = simple_strtoul(options + 5, &options, 0); | |
18a8bd94 YL |
147 | #ifdef CONFIG_FIX_EARLYCON_MEM |
148 | set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, port->mapbase & PAGE_MASK); | |
149 | port->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE); | |
150 | port->membase += port->mapbase & ~PAGE_MASK; | |
151 | #else | |
152 | port->membase = ioremap(port->mapbase, 64); | |
1da177e4 LT |
153 | if (!port->membase) { |
154 | printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n", | |
155 | __FUNCTION__, port->mapbase); | |
156 | return -ENOMEM; | |
157 | } | |
18a8bd94 | 158 | #endif |
1da177e4 LT |
159 | mmio = 1; |
160 | } else if (!strncmp(options, "io,", 3)) { | |
161 | port->iotype = UPIO_PORT; | |
162 | port->iobase = simple_strtoul(options + 3, &options, 0); | |
163 | mmio = 0; | |
164 | } else | |
165 | return -EINVAL; | |
166 | ||
167 | if ((options = strchr(options, ','))) { | |
168 | options++; | |
b2281abf | 169 | device->baud = simple_strtoul(options, NULL, 0); |
1da177e4 LT |
170 | length = min(strcspn(options, " "), sizeof(device->options)); |
171 | strncpy(device->options, options, length); | |
172 | } else { | |
173 | device->baud = probe_baud(port); | |
174 | snprintf(device->options, sizeof(device->options), "%u", | |
175 | device->baud); | |
176 | } | |
177 | ||
178 | printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n", | |
179 | mmio ? "MMIO" : "I/O port", | |
180 | mmio ? port->mapbase : (unsigned long) port->iobase, | |
181 | device->options); | |
182 | return 0; | |
183 | } | |
184 | ||
18a8bd94 YL |
185 | static struct console early_serial8250_console __initdata = { |
186 | .name = "uart", | |
187 | .write = early_serial8250_write, | |
188 | .flags = CON_PRINTBUFFER | CON_BOOT, | |
189 | .index = -1, | |
190 | }; | |
191 | ||
192 | static int __init early_serial8250_setup(char *options) | |
1da177e4 | 193 | { |
18a8bd94 | 194 | struct early_serial8250_device *device = &early_device; |
1da177e4 LT |
195 | int err; |
196 | ||
197 | if (device->port.membase || device->port.iobase) | |
198 | return 0; | |
199 | ||
200 | if ((err = parse_options(device, options)) < 0) | |
201 | return err; | |
202 | ||
203 | init_port(device); | |
204 | return 0; | |
205 | } | |
206 | ||
18a8bd94 | 207 | int __init setup_early_serial8250_console(char *cmdline) |
1da177e4 LT |
208 | { |
209 | char *options; | |
210 | int err; | |
211 | ||
18a8bd94 YL |
212 | options = strstr(cmdline, "uart8250,"); |
213 | if (!options) { | |
214 | options = strstr(cmdline, "uart,"); | |
215 | if (!options) | |
216 | return 0; | |
217 | } | |
1da177e4 LT |
218 | |
219 | options = strchr(cmdline, ',') + 1; | |
18a8bd94 | 220 | if ((err = early_serial8250_setup(options)) < 0) |
1da177e4 | 221 | return err; |
18a8bd94 YL |
222 | |
223 | register_console(&early_serial8250_console); | |
224 | ||
225 | return 0; | |
1da177e4 LT |
226 | } |
227 | ||
18a8bd94 | 228 | int __init serial8250_find_port_for_earlycon(void) |
1da177e4 | 229 | { |
18a8bd94 | 230 | struct early_serial8250_device *device = &early_device; |
1da177e4 | 231 | struct uart_port *port = &device->port; |
18a8bd94 YL |
232 | int line; |
233 | int ret; | |
1da177e4 | 234 | |
18a8bd94 YL |
235 | if (!device->port.membase && !device->port.iobase) |
236 | return -ENODEV; | |
1da177e4 | 237 | |
18a8bd94 | 238 | line = serial8250_find_port(port); |
1da177e4 | 239 | if (line < 0) |
18a8bd94 | 240 | return -ENODEV; |
1da177e4 | 241 | |
18a8bd94 YL |
242 | ret = update_console_cmdline("uart", 8250, |
243 | "ttyS", line, device->options); | |
244 | if (ret < 0) | |
245 | ret = update_console_cmdline("uart", 0, | |
246 | "ttyS", line, device->options); | |
1da177e4 | 247 | |
18a8bd94 | 248 | return ret; |
1da177e4 | 249 | } |
18a8bd94 YL |
250 | |
251 | early_param("earlycon", setup_early_serial8250_console); |