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  *      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
  77 static void __init putc(struct uart_port *port, int c)
  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
  92         uart_console_write(port, s, count, putc);
  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++;
 162                 device->baud = simple_strtoul(options, NULL, 0);
 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);