add get_timer to get accurate delay.

Change-Id: I99dbd6b3c84394744ca19759e7b7b8fcc6a180e7
Signed-off-by: QiaoChong <qiaochong@loongson.cn>

pmon/arch/mips/mips_machdep.c

@@ -268,6 +268,22 @@ void delay1(int microseconds)
 	};
 }
 
+unsigned int get_timer(unsigned int base)
+{
+	unsigned int clkperms;
+	static unsigned int high, low;
+	unsigned int now;
+	clkperms = tgt_pipefreq() / 2 /1000;
+	now = CPU_GetCOUNT();
+	if (!base)
+		high = 0;
+	else 
+		high += (now < low);
+	low = now;
+	return (high*0x100000000ULL+low)/clkperms - base;
+}
+
+
 u_int __res_randomid(void);
 u_int
 __res_randomid()

sys/arch/mips/include/cpu.h

@@ -460,6 +460,7 @@ void flushicache __P((void *, size_t));
 void flushdcache __P((void *, size_t));
 void syncicache __P((void *, size_t));
 void delay __P((int));
+unsigned int get_timer(unsigned int base);
 
 int	CPU_ConfigCache __P((void));
 void	CPU_SetWIRED __P((int));