--- a/arch/powerpc/platforms/Kconfig	
+++ b/arch/powerpc/platforms/Kconfig	
@@ -142,6 +142,10 @@ config GENERIC_IOMAP
 	bool
 	default n
 
+config RB_IOMAP
+	bool
+	default y if RB_PPC
+
 source "drivers/cpufreq/Kconfig"
 
 menu "CPU Frequency drivers"