8250_early.c

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/*
 * Early serial console for 8250/16550 devices
 *
 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
 *  Bjorn Helgaas <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
 * and on early_printk.c by Andi Kleen.
 *
 * This is for use before the serial driver has initialized, in
 * particular, before the UARTs have been discovered and named.
 * Instead of specifying the console device as, e.g., "ttyS0",
 * we locate the device directly by its MMIO or I/O port address.
 *
 * The user can specify the device directly, e.g.,
 *  earlycon=uart8250,io,0x3f8,9600n8
 *  earlycon=uart8250,mmio,0xff5e0000,115200n8
 *  earlycon=uart8250,mmio32,0xff5e0000,115200n8
 * or
 *  console=uart8250,io,0x3f8,9600n8
 *  console=uart8250,mmio,0xff5e0000,115200n8
 *  console=uart8250,mmio32,0xff5e0000,115200n8
 */

#include <linux/tty.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/serial_core.h>
#include <linux/serial_reg.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <asm/io.h>
#include <asm/serial.h>
#ifdef CONFIG_FIX_EARLYCON_MEM
#include <asm/pgtable.h>
#include <asm/fixmap.h>
#endif

struct early_serial8250_device {
    struct uart_port port;
    char options[16];       /* e.g., 115200n8 */
    unsigned int baud;
};

static struct early_serial8250_device early_device;

static unsigned int __init serial_in(struct uart_port *port, int offset)
{
    switch (port->iotype) {
    case UPIO_MEM:
        return readb(port->membase + offset);
    case UPIO_MEM32:
        return readl(port->membase + (offset << 2));
    case UPIO_PORT:
        return inb(port->iobase + offset);
    default:
        return 0;
    }
}

static void __init serial_out(struct uart_port *port, int offset, int value)
{
    switch (port->iotype) {
    case UPIO_MEM:
        writeb(value, port->membase + offset);
        break;
    case UPIO_MEM32:
        writel(value, port->membase + (offset << 2));
        break;
    case UPIO_PORT:
        outb(value, port->iobase + offset);
        break;
    }
}

#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

static void __init wait_for_xmitr(struct uart_port *port)
{
    unsigned int status;

    for (;;) {
        status = serial_in(port, UART_LSR);
        if ((status & BOTH_EMPTY) == BOTH_EMPTY)
            return;
        cpu_relax();
    }
}

static void __init serial_putc(struct uart_port *port, int c)
{
    wait_for_xmitr(port);
    serial_out(port, UART_TX, c);
}

static void __init early_serial8250_write(struct console *console,
                    const char *s, unsigned int count)
{
    struct uart_port *port = &early_device.port;
    unsigned int ier;

    /* Save the IER and disable interrupts */
    ier = serial_in(port, UART_IER);
    serial_out(port, UART_IER, 0);

    uart_console_write(port, s, count, serial_putc);

    /* Wait for transmitter to become empty and restore the IER */
    wait_for_xmitr(port);
    serial_out(port, UART_IER, ier);
}

static unsigned int __init probe_baud(struct uart_port *port)
{
    unsigned char lcr, dll, dlm;
    unsigned int quot;

    lcr = serial_in(port, UART_LCR);
    serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
    dll = serial_in(port, UART_DLL);
    dlm = serial_in(port, UART_DLM);
    serial_out(port, UART_LCR, lcr);

    quot = (dlm << 8) | dll;
    return (port->uartclk / 16) / quot;
}

static void __init init_port(struct early_serial8250_device *device)
{
    struct uart_port *port = &device->port;
    unsigned int divisor;
    unsigned char c;

    serial_out(port, UART_LCR, 0x3);    /* 8n1 */
    serial_out(port, UART_IER, 0);      /* no interrupt */
    serial_out(port, UART_FCR, 0);      /* no fifo */
    serial_out(port, UART_MCR, 0x3);    /* DTR + RTS */

    divisor = port->uartclk / (16 * device->baud);
    c = serial_in(port, UART_LCR);
    serial_out(port, UART_LCR, c | UART_LCR_DLAB);
    serial_out(port, UART_DLL, divisor & 0xff);
    serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
    serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
}

static int __init parse_options(struct early_serial8250_device *device,
                                char *options)
{
    struct uart_port *port = &device->port;
    int mmio, mmio32, length;

    if (!options)
        return -ENODEV;

    port->uartclk = BASE_BAUD * 16;

    mmio = !strncmp(options, "mmio,", 5);
    mmio32 = !strncmp(options, "mmio32,", 7);
    if (mmio || mmio32) {
        port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);
        port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),
                           &options, 0);
        if (mmio32)
            port->regshift = 2;
#ifdef CONFIG_FIX_EARLYCON_MEM
        set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
                    port->mapbase & PAGE_MASK);
        port->membase =
            (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
        port->membase += port->mapbase & ~PAGE_MASK;
#else
        port->membase = ioremap_nocache(port->mapbase, 64);
        if (!port->membase) {
            printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
                __func__,
                   (unsigned long long) port->mapbase);
            return -ENOMEM;
        }
#endif
    } else if (!strncmp(options, "io,", 3)) {
        port->iotype = UPIO_PORT;
        port->iobase = simple_strtoul(options + 3, &options, 0);
        mmio = 0;
    } else
        return -EINVAL;

    options = strchr(options, ',');
    if (options) {
        options++;
        device->baud = simple_strtoul(options, NULL, 0);
        length = min(strcspn(options, " "), sizeof(device->options));
        strncpy(device->options, options, length);
    } else {
        device->baud = probe_baud(port);
        snprintf(device->options, sizeof(device->options), "%u",
            device->baud);
    }

    if (mmio || mmio32)
        printk(KERN_INFO
               "Early serial console at MMIO%s 0x%llx (options '%s')\n",
            mmio32 ? "32" : "",
            (unsigned long long)port->mapbase,
            device->options);
    else
        printk(KERN_INFO
              "Early serial console at I/O port 0x%lx (options '%s')\n",
            port->iobase,
            device->options);

    return 0;
}

static struct console early_serial8250_console __initdata = {
    .name   = "uart",
    .write  = early_serial8250_write,
    .flags  = CON_PRINTBUFFER | CON_BOOT,
    .index  = -1,
};

static int __init early_serial8250_setup(char *options)
{
    struct early_serial8250_device *device = &early_device;
    int err;

    if (device->port.membase || device->port.iobase)
        return 0;

    err = parse_options(device, options);
    if (err < 0)
        return err;

    init_port(device);
    return 0;
}

int __init setup_early_serial8250_console(char *cmdline)
{
    char *options;
    int err;

    options = strstr(cmdline, "uart8250,");
    if (!options) {
        options = strstr(cmdline, "uart,");
        if (!options)
            return 0;
    }

    options = strchr(cmdline, ',') + 1;
    err = early_serial8250_setup(options);
    if (err < 0)
        return err;

    register_console(&early_serial8250_console);

    return 0;
}

int serial8250_find_port_for_earlycon(void)
{
    struct early_serial8250_device *device = &early_device;
    struct uart_port *port = &device->port;
    int line;
    int ret;

    if (!device->port.membase && !device->port.iobase)
        return -ENODEV;

    line = serial8250_find_port(port);
    if (line < 0)
        return -ENODEV;

    ret = update_console_cmdline("uart", 8250,
                 "ttyS", line, device->options);
    if (ret < 0)
        ret = update_console_cmdline("uart", 0,
                     "ttyS", line, device->options);

    return ret;
}

early_param("earlycon", setup_early_serial8250_console);