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, const char *s, unsigned int count)
  86 {
  87         struct uart_port *port = &early_device.port;
  88         unsigned int ier;
  89
  90         /* Save the IER and disable interrupts */
  91         ier = serial_in(port, UART_IER);
  92         serial_out(port, UART_IER, 0);
  93
  94         uart_console_write(port, s, count, serial_putc);
  95
  96         /* Wait for transmitter to become empty and restore the IER */
  97         wait_for_xmitr(port);
  98         serial_out(port, UART_IER, ier);
  99 }
 100
 101 static unsigned int __init probe_baud(struct uart_port *port)
 102 {
 103         unsigned char lcr, dll, dlm;
 104         unsigned int quot;
 105
 106         lcr = serial_in(port, UART_LCR);
 107         serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
 108         dll = serial_in(port, UART_DLL);
 109         dlm = serial_in(port, UART_DLM);
 110         serial_out(port, UART_LCR, lcr);
 111
 112         quot = (dlm << 8) | dll;
 113         return (port->uartclk / 16) / quot;
 114 }
 115
 116 static void __init init_port(struct early_serial8250_device *device)
 117 {
 118         struct uart_port *port = &device->port;
 119         unsigned int divisor;
 120         unsigned char c;
 121
 122         serial_out(port, UART_LCR, 0x3);        /* 8n1 */
 123         serial_out(port, UART_IER, 0);          /* no interrupt */
 124         serial_out(port, UART_FCR, 0);          /* no fifo */
 125         serial_out(port, UART_MCR, 0x3);        /* DTR + RTS */
 126
 127         divisor = port->uartclk / (16 * device->baud);
 128         c = serial_in(port, UART_LCR);
 129         serial_out(port, UART_LCR, c | UART_LCR_DLAB);
 130         serial_out(port, UART_DLL, divisor & 0xff);
 131         serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
 132         serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 133 }
 134
 135 static int __init parse_options(struct early_serial8250_device *device, char *options)
 136 {
 137         struct uart_port *port = &device->port;
 138         int mmio, length;
 139
 140         if (!options)
 141                 return -ENODEV;
 142
 143         port->uartclk = BASE_BAUD * 16;
 144         if (!strncmp(options, "mmio,", 5)) {
 145                 port->iotype = UPIO_MEM;
 146                 port->mapbase = simple_strtoul(options + 5, &options, 0);
 147 #ifdef CONFIG_FIX_EARLYCON_MEM
 148                 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, port->mapbase & PAGE_MASK);
 149                 port->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
 150                 port->membase += port->mapbase & ~PAGE_MASK;
 151 #else
 152                 port->membase = ioremap(port->mapbase, 64);
 153                 if (!port->membase) {
 154                         printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
 155                                 __FUNCTION__,
 156                                (unsigned long long)port->mapbase);
 157                         return -ENOMEM;
 158                 }
 159 #endif
 160                 mmio = 1;
 161         } else if (!strncmp(options, "io,", 3)) {
 162                 port->iotype = UPIO_PORT;
 163                 port->iobase = simple_strtoul(options + 3, &options, 0);
 164                 mmio = 0;
 165         } else
 166                 return -EINVAL;
 167
 168         if ((options = strchr(options, ','))) {
 169                 options++;
 170                 device->baud = simple_strtoul(options, NULL, 0);
 171                 length = min(strcspn(options, " "), sizeof(device->options));
 172                 strncpy(device->options, options, length);
 173         } else {
 174                 device->baud = probe_baud(port);
 175                 snprintf(device->options, sizeof(device->options), "%u",
 176                         device->baud);
 177         }
 178
 179         printk(KERN_INFO "Early serial console at %s 0x%llx (options '%s')\n",
 180                 mmio ? "MMIO" : "I/O port",
 181                 mmio ? (unsigned long long) port->mapbase
 182                      : (unsigned long long) port->iobase,
 183                 device->options);
 184         return 0;
 185 }
 186
 187 static struct console early_serial8250_console __initdata = {
 188         .name   = "uart",
 189         .write  = early_serial8250_write,
 190         .flags  = CON_PRINTBUFFER | CON_BOOT,
 191         .index  = -1,
 192 };
 193
 194 static int __init early_serial8250_setup(char *options)
 195 {
 196         struct early_serial8250_device *device = &early_device;
 197         int err;
 198
 199         if (device->port.membase || device->port.iobase)
 200                 return 0;
 201
 202         if ((err = parse_options(device, options)) < 0)
 203                 return err;
 204
 205         init_port(device);
 206         return 0;
 207 }
 208
 209 int __init setup_early_serial8250_console(char *cmdline)
 210 {
 211         char *options;
 212         int err;
 213
 214         options = strstr(cmdline, "uart8250,");
 215         if (!options) {
 216                 options = strstr(cmdline, "uart,");
 217                 if (!options)
 218                         return 0;
 219         }
 220
 221         options = strchr(cmdline, ',') + 1;
 222         if ((err = early_serial8250_setup(options)) < 0)
 223                 return err;
 224
 225         register_console(&early_serial8250_console);
 226
 227         return 0;
 228 }
 229
 230 int serial8250_find_port_for_earlycon(void)
 231 {
 232         struct early_serial8250_device *device = &early_device;
 233         struct uart_port *port = &device->port;
 234         int line;
 235         int ret;
 236
 237         if (!device->port.membase && !device->port.iobase)
 238                 return -ENODEV;
 239
 240         line = serial8250_find_port(port);
 241         if (line < 0)
 242                 return -ENODEV;
 243
 244         ret = update_console_cmdline("uart", 8250,
 245                              "ttyS", line, device->options);
 246         if (ret < 0)
 247                 ret = update_console_cmdline("uart", 0,
 248                                      "ttyS", line, device->options);
 249
 250         return ret;
 251 }
 252
 253 early_param("earlycon", setup_early_serial8250_console);