MIPS: Loongson: Add oprofile support

This kernel support is needed by the user-space tool:oprofile to profile
linux kernel or applications via loongson2 performance counters. you can
enable this driver via CONFIG_OPROFILE = y or m.

On Loongson2 there are two performance counters, each one can count 16
events respectively. when anyone of the performance counter overflows, an
interrupt will be generated and is routed to the IRQ MIPS_CPU_IRQ_BASE + 6.

Signed-off-by: Yanhua <yanh@lemote.com>
Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/oprofile/common.c b/arch/mips/oprofile/common.c
index 3bf3354..7832ad2 100644
--- a/arch/mips/oprofile/common.c
+++ b/arch/mips/oprofile/common.c
@@ -16,6 +16,7 @@
 
 extern struct op_mips_model op_model_mipsxx_ops __attribute__((weak));
 extern struct op_mips_model op_model_rm9000_ops __attribute__((weak));
+extern struct op_mips_model op_model_loongson2_ops __attribute__((weak));
 
 static struct op_mips_model *model;
 
@@ -93,6 +94,9 @@
 	case CPU_RM9000:
 		lmodel = &op_model_rm9000_ops;
 		break;
+	case CPU_LOONGSON2:
+		lmodel = &op_model_loongson2_ops;
+		break;
 	};
 
 	if (!lmodel)