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_nocache(port->mapbase, 64);
 157                 if (!port->membase) {
 158                         printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
 159                                 __func__,
 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);