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 * 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
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>
33 #include <linux/serial_8250.h>
34 #include <asm/io.h>
35 #include <asm/serial.h>
36 #ifdef CONFIG_FIX_EARLYCON_MEM
37 #include <asm/pgtable.h>
38 #include <asm/fixmap.h>
39 #endif
40
41 struct early_serial8250_device {
42 struct uart_port port;
43 char options[16]; /* e.g., 115200n8 */
44 unsigned int baud;
45 };
46
47 static struct early_serial8250_device early_device;
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
79 static void __init serial_putc(struct uart_port *port, int c)
80 {
81 wait_for_xmitr(port);
82 serial_out(port, UART_TX, c);
83 }
84
85 static void __init early_serial8250_write(struct console *console,
86 const char *s, unsigned int count)
87 {
88 struct uart_port *port = &early_device.port;
89 unsigned int ier;
90
91 /* Save the IER and disable interrupts */
92 ier = serial_in(port, UART_IER);
93 serial_out(port, UART_IER, 0);
94
95 uart_console_write(port, s, count, serial_putc);
96
97 /* Wait for transmitter to become empty and restore the IER */
98 wait_for_xmitr(port);
99 serial_out(port, UART_IER, ier);
100 }
101
102 static unsigned int __init probe_baud(struct uart_port *port)
103 {
104 unsigned char lcr, dll, dlm;
105 unsigned int quot;
106
107 lcr = serial_in(port, UART_LCR);
108 serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
109 dll = serial_in(port, UART_DLL);
110 dlm = serial_in(port, UART_DLM);
111 serial_out(port, UART_LCR, lcr);
112
113 quot = (dlm << 8) | dll;
114 return (port->uartclk / 16) / quot;
115 }
116
117 static void __init init_port(struct early_serial8250_device *device)
118 {
119 struct uart_port *port = &device->port;
120 unsigned int divisor;
121 unsigned char c;
122
123 serial_out(port, UART_LCR, 0x3); /* 8n1 */
124 serial_out(port, UART_IER, 0); /* no interrupt */
125 serial_out(port, UART_FCR, 0); /* no fifo */
126 serial_out(port, UART_MCR, 0x3); /* DTR + RTS */
127
128 divisor = port->uartclk / (16 * device->baud);
129 c = serial_in(port, UART_LCR);
130 serial_out(port, UART_LCR, c | UART_LCR_DLAB);
131 serial_out(port, UART_DLL, divisor & 0xff);
132 serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
133 serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
134 }
135
136 static int __init parse_options(struct early_serial8250_device *device,
137 char *options)
138 {
139 struct uart_port *port = &device->port;
140 int mmio, length;
141
142 if (!options)
143 return -ENODEV;
144
145 port->uartclk = BASE_BAUD * 16;
146 if (!strncmp(options, "mmio,", 5)) {
147 port->iotype = UPIO_MEM;
148 port->mapbase = simple_strtoul(options + 5, &options, 0);
149 #ifdef CONFIG_FIX_EARLYCON_MEM
150 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
151 port->mapbase & PAGE_MASK);
152 port->membase =
153 (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
154 port->membase += port->mapbase & ~PAGE_MASK;
155 #else
156 port->membase = ioremap_nocache(port->mapbase, 64);
157 if (!port->membase) {
158 printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
159 __func__,
160 (unsigned long long)port->mapbase);
161 return -ENOMEM;
162 }
163 #endif
164 mmio = 1;
165 } else if (!strncmp(options, "io,", 3)) {
166 port->iotype = UPIO_PORT;
167 port->iobase = simple_strtoul(options + 3, &options, 0);
168 mmio = 0;
169 } else
170 return -EINVAL;
171
172 options = strchr(options, ',');
173 if (options) {
174 options++;
175 device->baud = simple_strtoul(options, NULL, 0);
176 length = min(strcspn(options, " "), sizeof(device->options));
177 strncpy(device->options, options, length);
178 } else {
179 device->baud = probe_baud(port);
180 snprintf(device->options, sizeof(device->options), "%u",
181 device->baud);
182 }
183
184 printk(KERN_INFO "Early serial console at %s 0x%llx (options '%s')\n",
185 mmio ? "MMIO" : "I/O port",
186 mmio ? (unsigned long long) port->mapbase
187 : (unsigned long long) port->iobase,
188 device->options);
189 return 0;
190 }
191
192 static struct console early_serial8250_console __initdata = {
193 .name = "uart",
194 .write = early_serial8250_write,
195 .flags = CON_PRINTBUFFER | CON_BOOT,
196 .index = -1,
197 };
198
199 static int __init early_serial8250_setup(char *options)
200 {
201 struct early_serial8250_device *device = &early_device;
202 int err;
203
204 if (device->port.membase || device->port.iobase)
205 return 0;
206
207 err = parse_options(device, options);
208 if (err < 0)
209 return err;
210
211 init_port(device);
212 return 0;
213 }
214
215 int __init setup_early_serial8250_console(char *cmdline)
216 {
217 char *options;
218 int err;
219
220 options = strstr(cmdline, "uart8250,");
221 if (!options) {
222 options = strstr(cmdline, "uart,");
223 if (!options)
224 return 0;
225 }
226
227 options = strchr(cmdline, ',') + 1;
228 err = early_serial8250_setup(options);
229 if (err < 0)
230 return err;
231
232 register_console(&early_serial8250_console);
233
234 return 0;
235 }
236
237 int serial8250_find_port_for_earlycon(void)
238 {
239 struct early_serial8250_device *device = &early_device;
240 struct uart_port *port = &device->port;
241 int line;
242 int ret;
243
244 if (!device->port.membase && !device->port.iobase)
245 return -ENODEV;
246
247 line = serial8250_find_port(port);
248 if (line < 0)
249 return -ENODEV;
250
251 ret = update_console_cmdline("uart", 8250,
252 "ttyS", line, device->options);
253 if (ret < 0)
254 ret = update_console_cmdline("uart", 0,
255 "ttyS", line, device->options);
256
257 return ret;
258 }
259
260 early_param("earlycon", setup_early_serial8250_console);
261
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