diff --git a/arch/powerpc/sysdev/dart.h b/arch/powerpc/sysdev/dart.h
index 33ed9ed..c2d05763 100644
--- a/arch/powerpc/sysdev/dart.h
+++ b/arch/powerpc/sysdev/dart.h
@@ -20,29 +20,44 @@
 #define _POWERPC_SYSDEV_DART_H
 
 
-/* physical base of DART registers */
-#define DART_BASE        0xf8033000UL
-
 /* Offset from base to control register */
-#define DARTCNTL   0
-/* Offset from base to exception register */
-#define DARTEXCP   0x10
-/* Offset from base to TLB tag registers */
-#define DARTTAG    0x1000
+#define DART_CNTL	0
 
+/* Offset from base to exception register */
+#define DART_EXCP_U3	0x10
+/* Offset from base to TLB tag registers */
+#define DART_TAGS_U3	0x1000
+
+/* U4 registers */
+#define DART_BASE_U4	0x10
+#define DART_SIZE_U4	0x20
+#define DART_EXCP_U4	0x30
+#define DART_TAGS_U4	0x1000
 
 /* Control Register fields */
 
-/* base address of table (pfn) */
-#define DARTCNTL_BASE_MASK    0xfffff
-#define DARTCNTL_BASE_SHIFT   12
+/* U3 registers */
+#define DART_CNTL_U3_BASE_MASK	0xfffff
+#define DART_CNTL_U3_BASE_SHIFT	12
+#define DART_CNTL_U3_FLUSHTLB	0x400
+#define DART_CNTL_U3_ENABLE	0x200
+#define DART_CNTL_U3_SIZE_MASK	0x1ff
+#define DART_CNTL_U3_SIZE_SHIFT	0
 
-#define DARTCNTL_FLUSHTLB     0x400
-#define DARTCNTL_ENABLE       0x200
+/* U4 registers */
+#define DART_BASE_U4_BASE_MASK	0xffffff
+#define DART_BASE_U4_BASE_SHIFT	0
+#define DART_CNTL_U4_FLUSHTLB	0x20000000
+#define DART_CNTL_U4_ENABLE	0x80000000
+#define DART_SIZE_U4_SIZE_MASK	0x1fff
+#define DART_SIZE_U4_SIZE_SHIFT	0
+
+#define DART_REG(r)	(dart + ((r) >> 2))
+#define DART_IN(r)	(in_be32(DART_REG(r)))
+#define DART_OUT(r,v)	(out_be32(DART_REG(r), (v)))
+
 
 /* size of table in pages */
-#define DARTCNTL_SIZE_MASK    0x1ff
-#define DARTCNTL_SIZE_SHIFT   0
 
 
 /* DART table fields */