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 #ifdef  CONFIG_KDB
  42 #include <linux/kdb.h>
  43 static int  kdb_serial_line = -1;
  44 #endif  /* CONFIG_KDB */
  45
  46 struct early_serial8250_device {
  47         struct uart_port port;
  48         char options[16];               /* e.g., 115200n8 */
  49         unsigned int baud;
  50 };
  51
  52 static struct early_serial8250_device early_device;
  53
  54 static unsigned int __init serial_in(struct uart_port *port, int offset)
  55 {
  56         if (port->iotype == UPIO_MEM)
  57                 return readb(port->membase + offset);
  58         else
  59                 return inb(port->iobase + offset);
  60 }
  61
  62 static void __init serial_out(struct uart_port *port, int offset, int value)
  63 {
  64         if (port->iotype == UPIO_MEM)
  65                 writeb(value, port->membase + offset);
  66         else
  67                 outb(value, port->iobase + offset);
  68 }
  69
  70 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  71
  72 static void __init wait_for_xmitr(struct uart_port *port)
  73 {
  74         unsigned int status;
  75
  76         for (;;) {
  77                 status = serial_in(port, UART_LSR);
  78                 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
  79                         return;
  80                 cpu_relax();
  81         }
  82 }
  83
  84 static void __init serial_putc(struct uart_port *port, int c)
  85 {
  86         wait_for_xmitr(port);
  87         serial_out(port, UART_TX, c);
  88 }
  89
  90 static void __init early_serial8250_write(struct console *console,
  91                                         const char *s, unsigned int count)
  92 {
  93         struct uart_port *port = &early_device.port;
  94         unsigned int ier;
  95
  96         /* Save the IER and disable interrupts */
  97         ier = serial_in(port, UART_IER);
  98         serial_out(port, UART_IER, 0);
  99
 100         uart_console_write(port, s, count, serial_putc);
 101
 102         /* Wait for transmitter to become empty and restore the IER */
 103         wait_for_xmitr(port);
 104         serial_out(port, UART_IER, ier);
 105 }
 106
 107 static unsigned int __init probe_baud(struct uart_port *port)
 108 {
 109         unsigned char lcr, dll, dlm;
 110         unsigned int quot;
 111
 112         lcr = serial_in(port, UART_LCR);
 113         serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
 114         dll = serial_in(port, UART_DLL);
 115         dlm = serial_in(port, UART_DLM);
 116         serial_out(port, UART_LCR, lcr);
 117
 118         quot = (dlm << 8) | dll;
 119         return (port->uartclk / 16) / quot;
 120 }
 121
 122 static void __init init_port(struct early_serial8250_device *device)
 123 {
 124         struct uart_port *port = &device->port;
 125         unsigned int divisor;
 126         unsigned char c;
 127
 128         serial_out(port, UART_LCR, 0x3);        /* 8n1 */
 129         serial_out(port, UART_IER, 0);          /* no interrupt */
 130         serial_out(port, UART_FCR, 0);          /* no fifo */
 131         serial_out(port, UART_MCR, 0x3);        /* DTR + RTS */
 132
 133         divisor = port->uartclk / (16 * device->baud);
 134         c = serial_in(port, UART_LCR);
 135         serial_out(port, UART_LCR, c | UART_LCR_DLAB);
 136         serial_out(port, UART_DLL, divisor & 0xff);
 137         serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
 138         serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 139 }
 140
 141 static int __init parse_options(struct early_serial8250_device *device,
 142                                                                 char *options)
 143 {
 144         struct uart_port *port = &device->port;
 145         int mmio, length;
 146
 147         if (!options)
 148                 return -ENODEV;
 149
 150         port->uartclk = BASE_BAUD * 16;
 151         if (!strncmp(options, "mmio,", 5)) {
 152                 port->iotype = UPIO_MEM;
 153                 port->mapbase = simple_strtoul(options + 5, &options, 0);
 154 #ifdef CONFIG_FIX_EARLYCON_MEM
 155                 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
 156                                         port->mapbase & PAGE_MASK);
 157                 port->membase =
 158                         (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
 159                 port->membase += port->mapbase & ~PAGE_MASK;
 160 #else
 161                 port->membase = ioremap(port->mapbase, 64);
 162                 if (!port->membase) {
 163                         printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
 164                                 __FUNCTION__,
 165                                (unsigned long long)port->mapbase);
 166                         return -ENOMEM;
 167                 }
 168 #endif
 169                 mmio = 1;
 170         } else if (!strncmp(options, "io,", 3)) {
 171                 port->iotype = UPIO_PORT;
 172                 port->iobase = simple_strtoul(options + 3, &options, 0);
 173                 mmio = 0;
 174         } else
 175                 return -EINVAL;
 176
 177         options = strchr(options, ',');
 178         if (options) {
 179                 options++;
 180                 device->baud = simple_strtoul(options, NULL, 0);
 181                 length = min(strcspn(options, " "), sizeof(device->options));
 182                 strncpy(device->options, options, length);
 183         } else {
 184                 device->baud = probe_baud(port);
 185                 snprintf(device->options, sizeof(device->options), "%u",
 186                         device->baud);
 187         }
 188
 189         printk(KERN_INFO "Early serial console at %s 0x%llx (options '%s')\n",
 190                 mmio ? "MMIO" : "I/O port",
 191                 mmio ? (unsigned long long) port->mapbase
 192                      : (unsigned long long) port->iobase,
 193                 device->options);
 194         return 0;
 195 }
 196
 197 static struct console early_serial8250_console __initdata = {
 198         .name   = "uart",
 199         .write  = early_serial8250_write,
 200         .flags  = CON_PRINTBUFFER | CON_BOOT,
 201         .index  = -1,
 202 };
 203
 204 static int __init early_serial8250_setup(char *options)
 205 {
 206         struct early_serial8250_device *device = &early_device;
 207         int err;
 208
 209         if (device->port.membase || device->port.iobase)
 210                 return 0;
 211
 212         err = parse_options(device, options);
 213         if (err < 0)
 214                 return err;
 215
 216         init_port(device);
 217         return 0;
 218 }
 219
 220 int __init setup_early_serial8250_console(char *cmdline)
 221 {
 222         char *options;
 223         int err;
 224
 225         options = strstr(cmdline, "uart8250,");
 226         if (!options) {
 227                 options = strstr(cmdline, "uart,");
 228                 if (!options)
 229                         return 0;
 230         }
 231
 232         options = strchr(cmdline, ',') + 1;
 233         err = early_serial8250_setup(options);
 234         if (err < 0)
 235                 return err;
 236
 237         register_console(&early_serial8250_console);
 238
 239 #ifdef  CONFIG_KDB
 240         /*
 241          * Remember the line number of the first serial
 242          * console.  We'll make this the kdb serial console too.
 243          */
 244         if (kdb_serial_line == -1) {
 245                 kdb_serial_line = early_serial8250_console.index;
 246                 kdb_serial.io_type = early_device.port.iotype;
 247                 switch (early_device.port.iotype) {
 248                 case SERIAL_IO_MEM:
 249 #ifdef  SERIAL_IO_MEM32
 250                 case SERIAL_IO_MEM32:
 251 #endif
 252                         kdb_serial.iobase = (unsigned long)(early_device.port.membase);
 253                         kdb_serial.ioreg_shift = early_device.port.regshift;
 254                         break;
 255                 default:
 256                         kdb_serial.iobase = early_device.port.iobase;
 257                         kdb_serial.ioreg_shift = 0;
 258                         break;
 259                 }
 260         }
 261 #endif  /* CONFIG_KDB */
 262
 263         return 0;
 264 }
 265
 266 int serial8250_find_port_for_earlycon(void)
 267 {
 268         struct early_serial8250_device *device = &early_device;
 269         struct uart_port *port = &device->port;
 270         int line;
 271         int ret;
 272
 273         if (!device->port.membase && !device->port.iobase)
 274                 return -ENODEV;
 275
 276         line = serial8250_find_port(port);
 277         if (line < 0)
 278                 return -ENODEV;
 279
 280         ret = update_console_cmdline("uart", 8250,
 281                              "ttyS", line, device->options);
 282         if (ret < 0)
 283                 ret = update_console_cmdline("uart", 0,
 284                                      "ttyS", line, device->options);
 285
 286         return ret;
 287 }
 288
 289 early_param("earlycon", setup_early_serial8250_console);