Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | |
Russell King | d358788 | 2006-03-20 20:00:09 +0000 | [diff] [blame] | 77 | static void __init putc(struct uart_port *port, int c) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | |
Russell King | d358788 | 2006-03-20 20:00:09 +0000 | [diff] [blame] | 92 | uart_console_write(port, s, count, putc); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 93 | |
| 94 | /* Wait for transmitter to become empty and restore the IER */ |
| 95 | wait_for_xmitr(port); |
| 96 | serial_out(port, UART_IER, ier); |
| 97 | } |
| 98 | |
| 99 | static unsigned int __init probe_baud(struct uart_port *port) |
| 100 | { |
| 101 | unsigned char lcr, dll, dlm; |
| 102 | unsigned int quot; |
| 103 | |
| 104 | lcr = serial_in(port, UART_LCR); |
| 105 | serial_out(port, UART_LCR, lcr | UART_LCR_DLAB); |
| 106 | dll = serial_in(port, UART_DLL); |
| 107 | dlm = serial_in(port, UART_DLM); |
| 108 | serial_out(port, UART_LCR, lcr); |
| 109 | |
| 110 | quot = (dlm << 8) | dll; |
| 111 | return (port->uartclk / 16) / quot; |
| 112 | } |
| 113 | |
| 114 | static void __init init_port(struct early_uart_device *device) |
| 115 | { |
| 116 | struct uart_port *port = &device->port; |
| 117 | unsigned int divisor; |
| 118 | unsigned char c; |
| 119 | |
| 120 | serial_out(port, UART_LCR, 0x3); /* 8n1 */ |
| 121 | serial_out(port, UART_IER, 0); /* no interrupt */ |
| 122 | serial_out(port, UART_FCR, 0); /* no fifo */ |
| 123 | serial_out(port, UART_MCR, 0x3); /* DTR + RTS */ |
| 124 | |
| 125 | divisor = port->uartclk / (16 * device->baud); |
| 126 | c = serial_in(port, UART_LCR); |
| 127 | serial_out(port, UART_LCR, c | UART_LCR_DLAB); |
| 128 | serial_out(port, UART_DLL, divisor & 0xff); |
| 129 | serial_out(port, UART_DLM, (divisor >> 8) & 0xff); |
| 130 | serial_out(port, UART_LCR, c & ~UART_LCR_DLAB); |
| 131 | } |
| 132 | |
| 133 | static int __init parse_options(struct early_uart_device *device, char *options) |
| 134 | { |
| 135 | struct uart_port *port = &device->port; |
| 136 | int mapsize = 64; |
| 137 | int mmio, length; |
| 138 | |
| 139 | if (!options) |
| 140 | return -ENODEV; |
| 141 | |
| 142 | port->uartclk = BASE_BAUD * 16; |
| 143 | if (!strncmp(options, "mmio,", 5)) { |
| 144 | port->iotype = UPIO_MEM; |
| 145 | port->mapbase = simple_strtoul(options + 5, &options, 0); |
| 146 | port->membase = ioremap(port->mapbase, mapsize); |
| 147 | if (!port->membase) { |
| 148 | printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n", |
| 149 | __FUNCTION__, port->mapbase); |
| 150 | return -ENOMEM; |
| 151 | } |
| 152 | mmio = 1; |
| 153 | } else if (!strncmp(options, "io,", 3)) { |
| 154 | port->iotype = UPIO_PORT; |
| 155 | port->iobase = simple_strtoul(options + 3, &options, 0); |
| 156 | mmio = 0; |
| 157 | } else |
| 158 | return -EINVAL; |
| 159 | |
| 160 | if ((options = strchr(options, ','))) { |
| 161 | options++; |
Ben Dooks | b2281ab | 2005-11-03 21:07:37 +0000 | [diff] [blame] | 162 | device->baud = simple_strtoul(options, NULL, 0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 163 | length = min(strcspn(options, " "), sizeof(device->options)); |
| 164 | strncpy(device->options, options, length); |
| 165 | } else { |
| 166 | device->baud = probe_baud(port); |
| 167 | snprintf(device->options, sizeof(device->options), "%u", |
| 168 | device->baud); |
| 169 | } |
| 170 | |
| 171 | printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n", |
| 172 | mmio ? "MMIO" : "I/O port", |
| 173 | mmio ? port->mapbase : (unsigned long) port->iobase, |
| 174 | device->options); |
| 175 | return 0; |
| 176 | } |
| 177 | |
| 178 | static int __init early_uart_setup(struct console *console, char *options) |
| 179 | { |
| 180 | struct early_uart_device *device = &early_device; |
| 181 | int err; |
| 182 | |
| 183 | if (device->port.membase || device->port.iobase) |
| 184 | return 0; |
| 185 | |
| 186 | if ((err = parse_options(device, options)) < 0) |
| 187 | return err; |
| 188 | |
| 189 | init_port(device); |
| 190 | return 0; |
| 191 | } |
| 192 | |
| 193 | static struct console early_uart_console __initdata = { |
| 194 | .name = "uart", |
| 195 | .write = early_uart_write, |
| 196 | .setup = early_uart_setup, |
| 197 | .flags = CON_PRINTBUFFER, |
| 198 | .index = -1, |
| 199 | }; |
| 200 | |
| 201 | static int __init early_uart_console_init(void) |
| 202 | { |
| 203 | if (!early_uart_registered) { |
| 204 | register_console(&early_uart_console); |
| 205 | early_uart_registered = 1; |
| 206 | } |
| 207 | return 0; |
| 208 | } |
| 209 | console_initcall(early_uart_console_init); |
| 210 | |
| 211 | int __init early_serial_console_init(char *cmdline) |
| 212 | { |
| 213 | char *options; |
| 214 | int err; |
| 215 | |
| 216 | options = strstr(cmdline, "console=uart,"); |
| 217 | if (!options) |
| 218 | return -ENODEV; |
| 219 | |
| 220 | options = strchr(cmdline, ',') + 1; |
| 221 | if ((err = early_uart_setup(NULL, options)) < 0) |
| 222 | return err; |
| 223 | return early_uart_console_init(); |
| 224 | } |
| 225 | |
| 226 | static int __init early_uart_console_switch(void) |
| 227 | { |
| 228 | struct early_uart_device *device = &early_device; |
| 229 | struct uart_port *port = &device->port; |
| 230 | int mmio, line; |
| 231 | |
| 232 | if (!(early_uart_console.flags & CON_ENABLED)) |
| 233 | return 0; |
| 234 | |
| 235 | /* Try to start the normal driver on a matching line. */ |
| 236 | mmio = (port->iotype == UPIO_MEM); |
| 237 | line = serial8250_start_console(port, device->options); |
| 238 | if (line < 0) |
| 239 | printk("No ttyS device at %s 0x%lx for console\n", |
| 240 | mmio ? "MMIO" : "I/O port", |
| 241 | mmio ? port->mapbase : |
| 242 | (unsigned long) port->iobase); |
| 243 | |
| 244 | unregister_console(&early_uart_console); |
| 245 | if (mmio) |
| 246 | iounmap(port->membase); |
| 247 | |
| 248 | return 0; |
| 249 | } |
| 250 | late_initcall(early_uart_console_switch); |