microblaze_v8: early_printk support

/*

 * Early printk support for Microblaze.

 *

 * Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>

 * Copyright (C) 2007-2009 PetaLogix

 * Copyright (C) 2003-2006 Yasushi SHOJI <yashi@atmark-techno.com>

 *

 * 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;

static void early_printk_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 = 10000;

	/* 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_write(struct console *unused,

					const char *s, unsigned n)

{

	while (*s && n-- > 0) {

		early_printk_putc(*s);

		if (*s == '\n')

			early_printk_putc('\r');

		s++;

	}

}

static struct console early_serial_console = {

	.name = "earlyser",

	.write = early_printk_write,

	.flags = CON_PRINTBUFFER,

	.index = -1,

};

static struct console *early_console = &early_serial_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)

{

	if (early_console_initialized)

		return 1;

	base_addr = early_uartlite_console();

	if (base_addr) {

		early_console_initialized = 1;

		early_printk("early_printk_console is enabled at 0x%08x\n",

							base_addr);

		/* register_console(early_console); */

		return 0;

	} else

		return 1;

}

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;

}