MIPS: Loongson: Add new early_printk implmentation

This patch is based on the implementation in the lm2e-fixes branch of
Philippe's git://git.linux-cisco.org/linux-mips.git and the
malta-specific early_printk implementation.
Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/lemote/lm2e/Makefile

@@ -4,4 +4,9 @@
 
 obj-y += setup.o prom.o reset.o irq.o pci.o bonito-irq.o mem.o
 
+#
+# Early printk support
+#
+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
+
 EXTRA_CFLAGS += -Werror

arch/mips/lemote/lm2e/early_printk.c

+/*  early printk support
+ *
+ *  Copyright (c) 2009 Philippe Vachon <philippe@cowpig.ca>
+ *  Copyright (C) 2009 Lemote Inc. & Insititute of Computing Technology
+ *  Author: Wu Zhangjin, wuzj@lemote.com
+ *
+ *  This program is free software; you can redistribute  it and/or modify it
+ *  under  the terms of  the GNU General  Public License as published by the
+ *  Free Software Foundation;  either version 2 of the  License, or (at your
+ *  option) any later version.
+ */
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/serial_reg.h>
+
+#include <asm/mips-boards/bonito64.h>
+
+#define UART_BASE (BONITO_PCIIO_BASE + 0x3f8)
+
+#define PORT(base, offset) (u8 *)(base + offset)
+
+static inline unsigned int serial_in(phys_addr_t base, int offset)
+{
+	return readb(PORT(base, offset));
+}
+
+static inline void serial_out(phys_addr_t base, int offset, int value)
+{
+	writeb(value, PORT(base, offset));
+}
+
+void prom_putchar(char c)
+{
+	phys_addr_t uart_base =
+		(phys_addr_t) ioremap_nocache(UART_BASE, 8);
+
+	while ((serial_in(uart_base, UART_LSR) & UART_LSR_THRE) == 0)
+		;
+
+	serial_out(uart_base, UART_TX, c);
+}