early_printk.c

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/*
 * Early printk support for Microblaze.
 *
 * Copyright (C) 2007-2009 Michal Simek <[email protected]>
 * Copyright (C) 2007-2009 PetaLogix
 * Copyright (C) 2003-2006 Yasushi SHOJI <[email protected]>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/tty.h>
#include <linux/io.h>
#include <asm/processor.h>
#include <linux/fcntl.h>
#include <asm/setup.h>
#include <asm/prom.h>

static u32 early_console_initialized;
static u32 base_addr;

#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
static void early_printk_uartlite_putc(char c)
{
    /*
     * Limit how many times we'll spin waiting for TX FIFO status.
     * This will prevent lockups if the base address is incorrectly
     * set, or any other issue on the UARTLITE.
     * This limit is pretty arbitrary, unless we are at about 10 baud
     * we'll never timeout on a working UART.
     */

    unsigned retries = 1000000;
    /* read status bit - 0x8 offset */
    while (--retries && (in_be32(base_addr + 8) & (1 << 3)))
        ;

    /* Only attempt the iowrite if we didn't timeout */
    /* write to TX_FIFO - 0x4 offset */
    if (retries)
        out_be32(base_addr + 4, c & 0xff);
}

static void early_printk_uartlite_write(struct console *unused,
                    const char *s, unsigned n)
{
    while (*s && n-- > 0) {
        if (*s == '\n')
            early_printk_uartlite_putc('\r');
        early_printk_uartlite_putc(*s);
        s++;
    }
}

static struct console early_serial_uartlite_console = {
    .name = "earlyser",
    .write = early_printk_uartlite_write,
    .flags = CON_PRINTBUFFER | CON_BOOT,
    .index = -1,
};
#endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */

#ifdef CONFIG_SERIAL_8250_CONSOLE
static void early_printk_uart16550_putc(char c)
{
    /*
     * Limit how many times we'll spin waiting for TX FIFO status.
     * This will prevent lockups if the base address is incorrectly
     * set, or any other issue on the UARTLITE.
     * This limit is pretty arbitrary, unless we are at about 10 baud
     * we'll never timeout on a working UART.
     */

    #define UART_LSR_TEMT   0x40 /* Transmitter empty */
    #define UART_LSR_THRE   0x20 /* Transmit-hold-register empty */
    #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

    unsigned retries = 10000;

    while (--retries &&
        !((in_be32(base_addr + 0x14) & BOTH_EMPTY) == BOTH_EMPTY))
        ;

    if (retries)
        out_be32(base_addr, c & 0xff);
}

static void early_printk_uart16550_write(struct console *unused,
                    const char *s, unsigned n)
{
    while (*s && n-- > 0) {
        if (*s == '\n')
            early_printk_uart16550_putc('\r');
        early_printk_uart16550_putc(*s);
        s++;
    }
}

static struct console early_serial_uart16550_console = {
    .name = "earlyser",
    .write = early_printk_uart16550_write,
    .flags = CON_PRINTBUFFER | CON_BOOT,
    .index = -1,
};
#endif /* CONFIG_SERIAL_8250_CONSOLE */

static struct console *early_console;

void early_printk(const char *fmt, ...)
{
    char buf[512];
    int n;
    va_list ap;

    if (early_console_initialized) {
        va_start(ap, fmt);
        n = vscnprintf(buf, 512, fmt, ap);
        early_console->write(early_console, buf, n);
        va_end(ap);
    }
}

int __init setup_early_printk(char *opt)
{
    int version = 0;

    if (early_console_initialized)
        return 1;

    base_addr = of_early_console(&version);
    if (base_addr) {
#ifdef CONFIG_MMU
        early_console_reg_tlb_alloc(base_addr);
#endif
        switch (version) {
#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
        case UARTLITE:
            printk(KERN_INFO "Early console on uartlite "
                        "at 0x%08x\n", base_addr);
            early_console = &early_serial_uartlite_console;
            break;
#endif
#ifdef CONFIG_SERIAL_8250_CONSOLE
        case UART16550:
            printk(KERN_INFO "Early console on uart16650 "
                        "at 0x%08x\n", base_addr);
            early_console = &early_serial_uart16550_console;
            break;
#endif
        default:
            printk(KERN_INFO  "Unsupported early console %d\n",
                                version);
            return 1;
        }

        register_console(early_console);
        early_console_initialized = 1;
        return 0;
    }
    return 1;
}

/* Remap early console to virtual address and do not allocate one TLB
 * only for early console because of performance degression */
void __init remap_early_printk(void)
{
    if (!early_console_initialized || !early_console)
        return;
    printk(KERN_INFO "early_printk_console remapping from 0x%x to ",
                                base_addr);
    base_addr = (u32) ioremap(base_addr, PAGE_SIZE);
    printk(KERN_CONT "0x%x\n", base_addr);

#ifdef CONFIG_MMU
    /*
     * Early console is on the top of skipped TLB entries
     * decrease tlb_skip size ensure that hardcoded TLB entry will be
     * used by generic algorithm
     * FIXME check if early console mapping is on the top by rereading
     * TLB entry and compare baseaddr
     *  mts  rtlbx, (tlb_skip - 1)
     *  nop
     *  mfs  rX, rtlblo
     *  nop
     *  cmp rX, orig_base_addr
     */
    tlb_skip -= 1;
#endif
}

void __init disable_early_printk(void)
{
    if (!early_console_initialized || !early_console)
        return;
    printk(KERN_WARNING "disabling early console\n");
    unregister_console(early_console);
    early_console_initialized = 0;
}