8250_early: coding style
[linux-3.10.git] / drivers / serial / 8250_early.c
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(port->mapbase, 64);
157                 if (!port->membase) {
158                         printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
159                                 __FUNCTION__,
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);