MIPS: add board qemu-mips64 support

Both big-endian and little-endian are tested with below commands:
Rom version: (Default, Now we config it as rom version)
qemu-system-mips64el -M mips -bios u-boot.bin -cpu MIPS64R2-generic -nographic
qemu-system-mips64 -M mips -bios u-boot.bin -cpu MIPS64R2-generic -nographic
Ram version:
qemu-system-mips64el -M mips -cpu MIPS64R2-generic -kernel u-boot -nographic
qemu-system-mips64 -M mips -cpu MIPS64R2-generic -kernel u-boot -nographic

Signed-off-by: Zhizhou Zhang <etou.zh@gmail.com>
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/cpu/mips64/time.c b/arch/mips/cpu/mips64/time.c
new file mode 100644
index 0000000..5154280
--- /dev/null
+++ b/arch/mips/cpu/mips64/time.c
@@ -0,0 +1,87 @@
+/*
+ * (C) Copyright 2003
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <asm/mipsregs.h>
+
+static unsigned long timestamp;
+
+/* how many counter cycles in a jiffy */
+#define CYCLES_PER_JIFFY	 \
+	(CONFIG_SYS_MIPS_TIMER_FREQ + CONFIG_SYS_HZ / 2) / CONFIG_SYS_HZ
+
+/*
+ * timer without interrupts
+ */
+
+int timer_init(void)
+{
+	/* Set up the timer for the first expiration. */
+	timestamp = 0;
+	write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
+
+	return 0;
+}
+
+ulong get_timer(ulong base)
+{
+	unsigned int count;
+	unsigned int expirelo = read_c0_compare();
+
+	/* Check to see if we have missed any timestamps. */
+	count = read_c0_count();
+	while ((count - expirelo) < 0x7fffffff) {
+		expirelo += CYCLES_PER_JIFFY;
+		timestamp++;
+	}
+	write_c0_compare(expirelo);
+
+	return timestamp - base;
+}
+
+void __udelay(unsigned long usec)
+{
+	unsigned int tmo;
+
+	tmo = read_c0_count() + (usec * (CONFIG_SYS_MIPS_TIMER_FREQ / 1000000));
+	while ((tmo - read_c0_count()) < 0x7fffffff)
+		/*NOP*/;
+}
+
+/*
+ * This function is derived from PowerPC code (read timebase as long long).
+ * On MIPS it just returns the timer value.
+ */
+unsigned long long get_ticks(void)
+{
+	return get_timer(0);
+}
+
+/*
+ * This function is derived from PowerPC code (timebase clock frequency).
+ * On MIPS it returns the number of timer ticks per second.
+ */
+ulong get_tbclk(void)
+{
+	return CONFIG_SYS_HZ;
+}