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 * earlycon=uart8250,mmio32,0xff5e0000,115200n8
23 * or
24 * console=uart8250,io,0x3f8,9600n8
25 * console=uart8250,mmio,0xff5e0000,115200n8
26 * console=uart8250,mmio32,0xff5e0000,115200n8
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 <linux/serial_8250.h>
36 #include <asm/io.h>
37 #include <asm/serial.h>
38 #ifdef CONFIG_FIX_EARLYCON_MEM
39 #include <asm/pgtable.h>
40 #include <asm/fixmap.h>
41 #endif
42
43 struct early_serial8250_device {
44 struct uart_port port;
45 char options[16]; /* e.g., 115200n8 */
46 unsigned int baud;
47 };
48
49 static struct early_serial8250_device early_device;
50
serial_in(struct uart_port * port,int offset)51 static unsigned int __init serial_in(struct uart_port *port, int offset)
52 {
53 switch (port->iotype) {
54 case UPIO_MEM:
55 return readb(port->membase + offset);
56 case UPIO_MEM32:
57 return readl(port->membase + (offset << 2));
58 case UPIO_PORT:
59 return inb(port->iobase + offset);
60 default:
61 return 0;
62 }
63 }
64
serial_out(struct uart_port * port,int offset,int value)65 static void __init serial_out(struct uart_port *port, int offset, int value)
66 {
67 switch (port->iotype) {
68 case UPIO_MEM:
69 writeb(value, port->membase + offset);
70 break;
71 case UPIO_MEM32:
72 writel(value, port->membase + (offset << 2));
73 break;
74 case UPIO_PORT:
75 outb(value, port->iobase + offset);
76 break;
77 }
78 }
79
80 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
81
wait_for_xmitr(struct uart_port * port)82 static void __init wait_for_xmitr(struct uart_port *port)
83 {
84 unsigned int status;
85
86 for (;;) {
87 status = serial_in(port, UART_LSR);
88 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
89 return;
90 cpu_relax();
91 }
92 }
93
serial_putc(struct uart_port * port,int c)94 static void __init serial_putc(struct uart_port *port, int c)
95 {
96 wait_for_xmitr(port);
97 serial_out(port, UART_TX, c);
98 }
99
early_serial8250_write(struct console * console,const char * s,unsigned int count)100 static void __init early_serial8250_write(struct console *console,
101 const char *s, unsigned int count)
102 {
103 struct uart_port *port = &early_device.port;
104 unsigned int ier;
105
106 /* Save the IER and disable interrupts */
107 ier = serial_in(port, UART_IER);
108 serial_out(port, UART_IER, 0);
109
110 uart_console_write(port, s, count, serial_putc);
111
112 /* Wait for transmitter to become empty and restore the IER */
113 wait_for_xmitr(port);
114 serial_out(port, UART_IER, ier);
115 }
116
probe_baud(struct uart_port * port)117 static unsigned int __init probe_baud(struct uart_port *port)
118 {
119 unsigned char lcr, dll, dlm;
120 unsigned int quot;
121
122 lcr = serial_in(port, UART_LCR);
123 serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
124 dll = serial_in(port, UART_DLL);
125 dlm = serial_in(port, UART_DLM);
126 serial_out(port, UART_LCR, lcr);
127
128 quot = (dlm << 8) | dll;
129 return (port->uartclk / 16) / quot;
130 }
131
init_port(struct early_serial8250_device * device)132 static void __init init_port(struct early_serial8250_device *device)
133 {
134 struct uart_port *port = &device->port;
135 unsigned int divisor;
136 unsigned char c;
137
138 serial_out(port, UART_LCR, 0x3); /* 8n1 */
139 serial_out(port, UART_IER, 0); /* no interrupt */
140 serial_out(port, UART_FCR, 0); /* no fifo */
141 serial_out(port, UART_MCR, 0x3); /* DTR + RTS */
142
143 divisor = port->uartclk / (16 * device->baud);
144 c = serial_in(port, UART_LCR);
145 serial_out(port, UART_LCR, c | UART_LCR_DLAB);
146 serial_out(port, UART_DLL, divisor & 0xff);
147 serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
148 serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
149 }
150
parse_options(struct early_serial8250_device * device,char * options)151 static int __init parse_options(struct early_serial8250_device *device,
152 char *options)
153 {
154 struct uart_port *port = &device->port;
155 int mmio, mmio32, length;
156
157 if (!options)
158 return -ENODEV;
159
160 port->uartclk = BASE_BAUD * 16;
161
162 mmio = !strncmp(options, "mmio,", 5);
163 mmio32 = !strncmp(options, "mmio32,", 7);
164 if (mmio || mmio32) {
165 port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);
166 port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),
167 &options, 0);
168 if (mmio32)
169 port->regshift = 2;
170 #ifdef CONFIG_FIX_EARLYCON_MEM
171 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
172 port->mapbase & PAGE_MASK);
173 port->membase =
174 (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
175 port->membase += port->mapbase & ~PAGE_MASK;
176 #else
177 port->membase = ioremap_nocache(port->mapbase, 64);
178 if (!port->membase) {
179 printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
180 __func__,
181 (unsigned long long) port->mapbase);
182 return -ENOMEM;
183 }
184 #endif
185 } else if (!strncmp(options, "io,", 3)) {
186 port->iotype = UPIO_PORT;
187 port->iobase = simple_strtoul(options + 3, &options, 0);
188 mmio = 0;
189 } else
190 return -EINVAL;
191
192 options = strchr(options, ',');
193 if (options) {
194 options++;
195 device->baud = simple_strtoul(options, NULL, 0);
196 length = min(strcspn(options, " "), sizeof(device->options));
197 strncpy(device->options, options, length);
198 } else {
199 device->baud = probe_baud(port);
200 snprintf(device->options, sizeof(device->options), "%u",
201 device->baud);
202 }
203
204 if (mmio || mmio32)
205 printk(KERN_INFO
206 "Early serial console at MMIO%s 0x%llx (options '%s')\n",
207 mmio32 ? "32" : "",
208 (unsigned long long)port->mapbase,
209 device->options);
210 else
211 printk(KERN_INFO
212 "Early serial console at I/O port 0x%lx (options '%s')\n",
213 port->iobase,
214 device->options);
215
216 return 0;
217 }
218
219 static struct console early_serial8250_console __initdata = {
220 .name = "uart",
221 .write = early_serial8250_write,
222 .flags = CON_PRINTBUFFER | CON_BOOT,
223 .index = -1,
224 };
225
early_serial8250_setup(char * options)226 static int __init early_serial8250_setup(char *options)
227 {
228 struct early_serial8250_device *device = &early_device;
229 int err;
230
231 if (device->port.membase || device->port.iobase)
232 return 0;
233
234 err = parse_options(device, options);
235 if (err < 0)
236 return err;
237
238 init_port(device);
239 return 0;
240 }
241
setup_early_serial8250_console(char * cmdline)242 int __init setup_early_serial8250_console(char *cmdline)
243 {
244 char *options;
245 int err;
246
247 options = strstr(cmdline, "uart8250,");
248 if (!options) {
249 options = strstr(cmdline, "uart,");
250 if (!options)
251 return 0;
252 }
253
254 options = strchr(cmdline, ',') + 1;
255 err = early_serial8250_setup(options);
256 if (err < 0)
257 return err;
258
259 register_console(&early_serial8250_console);
260
261 return 0;
262 }
263
serial8250_find_port_for_earlycon(void)264 int serial8250_find_port_for_earlycon(void)
265 {
266 struct early_serial8250_device *device = &early_device;
267 struct uart_port *port = &device->port;
268 int line;
269 int ret;
270
271 if (!device->port.membase && !device->port.iobase)
272 return -ENODEV;
273
274 line = serial8250_find_port(port);
275 if (line < 0)
276 return -ENODEV;
277
278 ret = update_console_cmdline("uart", 8250,
279 "ttyS", line, device->options);
280 if (ret < 0)
281 ret = update_console_cmdline("uart", 0,
282 "ttyS", line, device->options);
283
284 return ret;
285 }
286
287 early_param("earlycon", setup_early_serial8250_console);
288