drivers/tty/serial/8250/8250_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  *      earlycon=uart8250,mmio32,0xff5e0000,115200n8
  23  * or
  24  *      console=uart8250,io,0x3f8,9600n8
  25  *      console=uart8250,mmio,0xff5e0000,115200n8
  26  *      console=uart8250,mmio32,0xff5e0000,115200n8
  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 <linux/serial_8250.h>
  36 #include <asm/io.h>
  37 #include <asm/serial.h>
  38 #ifdef CONFIG_FIX_EARLYCON_MEM
  39 #include <asm/pgtable.h>
  40 #include <asm/fixmap.h>
  41 #endif
  42
  43 struct early_serial8250_device {
  44         struct uart_port port;
  45         char options[16];               /* e.g., 115200n8 */
  46         unsigned int baud;
  47 };
  48
  49 static struct early_serial8250_device early_device;
  50
  51 static unsigned int __init serial_in(struct uart_port *port, int offset)
  52 {
  53         switch (port->iotype) {
  54         case UPIO_MEM:
  55                 return readb(port->membase + offset);
  56         case UPIO_MEM32:
  57                 return readl(port->membase + (offset << 2));
  58         case UPIO_PORT:
  59                 return inb(port->iobase + offset);
  60         default:
  61                 return 0;
  62         }
  63 }
  64
  65 static void __init serial_out(struct uart_port *port, int offset, int value)
  66 {
  67         switch (port->iotype) {
  68         case UPIO_MEM:
  69                 writeb(value, port->membase + offset);
  70                 break;
  71         case UPIO_MEM32:
  72                 writel(value, port->membase + (offset << 2));
  73                 break;
  74         case UPIO_PORT:
  75                 outb(value, port->iobase + offset);
  76                 break;
  77         }
  78 }
  79
  80 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  81
  82 static void __init wait_for_xmitr(struct uart_port *port)
  83 {
  84         unsigned int status;
  85
  86         for (;;) {
  87                 status = serial_in(port, UART_LSR);
  88                 if ((status & BOTH_EMPTY) == BOTH_EMPTY)
  89                         return;
  90                 cpu_relax();
  91         }
  92 }
  93
  94 static void __init serial_putc(struct uart_port *port, int c)
  95 {
  96         wait_for_xmitr(port);
  97         serial_out(port, UART_TX, c);
  98 }
  99
 100 static void __init early_serial8250_write(struct console *console,
 101                                         const char *s, unsigned int count)
 102 {
 103         struct uart_port *port = &early_device.port;
 104         unsigned int ier;
 105
 106         /* Save the IER and disable interrupts */
 107         ier = serial_in(port, UART_IER);
 108         serial_out(port, UART_IER, 0);
 109
 110         uart_console_write(port, s, count, serial_putc);
 111
 112         /* Wait for transmitter to become empty and restore the IER */
 113         wait_for_xmitr(port);
 114         serial_out(port, UART_IER, ier);
 115 }
 116
 117 static unsigned int __init probe_baud(struct uart_port *port)
 118 {
 119         unsigned char lcr, dll, dlm;
 120         unsigned int quot;
 121
 122         lcr = serial_in(port, UART_LCR);
 123         serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
 124         dll = serial_in(port, UART_DLL);
 125         dlm = serial_in(port, UART_DLM);
 126         serial_out(port, UART_LCR, lcr);
 127
 128         quot = (dlm << 8) | dll;
 129         return (port->uartclk / 16) / quot;
 130 }
 131
 132 static void __init init_port(struct early_serial8250_device *device)
 133 {
 134         struct uart_port *port = &device->port;
 135         unsigned int divisor;
 136         unsigned char c;
 137
 138         serial_out(port, UART_LCR, 0x3);        /* 8n1 */
 139         serial_out(port, UART_IER, 0);          /* no interrupt */
 140         serial_out(port, UART_FCR, 0);          /* no fifo */
 141         serial_out(port, UART_MCR, 0x3);        /* DTR + RTS */
 142
 143         divisor = port->uartclk / (16 * device->baud);
 144         c = serial_in(port, UART_LCR);
 145         serial_out(port, UART_LCR, c | UART_LCR_DLAB);
 146         serial_out(port, UART_DLL, divisor & 0xff);
 147         serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
 148         serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 149 }
 150
 151 static int __init parse_options(struct early_serial8250_device *device,
 152                                                                 char *options)
 153 {
 154         struct uart_port *port = &device->port;
 155         int mmio, mmio32, length;
 156
 157         if (!options)
 158                 return -ENODEV;
 159
 160         port->uartclk = BASE_BAUD * 16;
 161
 162         mmio = !strncmp(options, "mmio,", 5);
 163         mmio32 = !strncmp(options, "mmio32,", 7);
 164         if (mmio || mmio32) {
 165                 port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);
 166                 port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),
 167                                                &options, 0);
 168                 if (mmio32)
 169                         port->regshift = 2;
 170 #ifdef CONFIG_FIX_EARLYCON_MEM
 171                 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
 172                                         port->mapbase & PAGE_MASK);
 173                 port->membase =
 174                         (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
 175                 port->membase += port->mapbase & ~PAGE_MASK;
 176 #else
 177                 port->membase = ioremap_nocache(port->mapbase, 64);
 178                 if (!port->membase) {
 179                         printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
 180                                 __func__,
 181                                (unsigned long long) port->mapbase);
 182                         return -ENOMEM;
 183                 }
 184 #endif
 185         } else if (!strncmp(options, "io,", 3)) {
 186                 port->iotype = UPIO_PORT;
 187                 port->iobase = simple_strtoul(options + 3, &options, 0);
 188                 mmio = 0;
 189         } else
 190                 return -EINVAL;
 191
 192         options = strchr(options, ',');
 193         if (options) {
 194                 options++;
 195                 device->baud = simple_strtoul(options, NULL, 0);
 196                 length = min(strcspn(options, " "), sizeof(device->options));
 197                 strncpy(device->options, options, length);
 198         } else {
 199                 device->baud = probe_baud(port);
 200                 snprintf(device->options, sizeof(device->options), "%u",
 201                         device->baud);
 202         }
 203
 204         if (mmio || mmio32)
 205                 printk(KERN_INFO
 206                        "Early serial console at MMIO%s 0x%llx (options '%s')\n",
 207                         mmio32 ? "32" : "",
 208                         (unsigned long long)port->mapbase,
 209                         device->options);
 210         else
 211                 printk(KERN_INFO
 212                       "Early serial console at I/O port 0x%lx (options '%s')\n",
 213                         port->iobase,
 214                         device->options);
 215
 216         return 0;
 217 }
 218
 219 static struct console early_serial8250_console __initdata = {
 220         .name   = "uart",
 221         .write  = early_serial8250_write,
 222         .flags  = CON_PRINTBUFFER | CON_BOOT,
 223         .index  = -1,
 224 };
 225
 226 static int __init early_serial8250_setup(char *options)
 227 {
 228         struct early_serial8250_device *device = &early_device;
 229         int err;
 230
 231         if (device->port.membase || device->port.iobase)
 232                 return 0;
 233
 234         err = parse_options(device, options);
 235         if (err < 0)
 236                 return err;
 237
 238         init_port(device);
 239         return 0;
 240 }
 241
 242 int __init setup_early_serial8250_console(char *cmdline)
 243 {
 244         char *options;
 245         int err;
 246
 247         options = strstr(cmdline, "uart8250,");
 248         if (!options) {
 249                 options = strstr(cmdline, "uart,");
 250                 if (!options)
 251                         return 0;
 252         }
 253
 254         options = strchr(cmdline, ',') + 1;
 255         err = early_serial8250_setup(options);
 256         if (err < 0)
 257                 return err;
 258
 259         register_console(&early_serial8250_console);
 260
 261         return 0;
 262 }
 263
 264 int serial8250_find_port_for_earlycon(void)
 265 {
 266         struct early_serial8250_device *device = &early_device;
 267         struct uart_port *port = &device->port;
 268         int line;
 269         int ret;
 270
 271         if (!device->port.membase && !device->port.iobase)
 272                 return -ENODEV;
 273
 274         line = serial8250_find_port(port);
 275         if (line < 0)
 276                 return -ENODEV;
 277
 278         ret = update_console_cmdline("uart", 8250,
 279                              "ttyS", line, device->options);
 280         if (ret < 0)
 281                 ret = update_console_cmdline("uart", 0,
 282                                      "ttyS", line, device->options);
 283
 284         return ret;
 285 }
 286
 287 early_param("earlycon", setup_early_serial8250_console);