powerpc/mm/radix: Add dummy radix_enabled()

In this patch we add the radix Kconfig and conditional check.
radix_enabled() is written to always return 0 here. Once we have all
needed radix changes added, we will update this to an mmu_feature check.

We need to add this early so that we can get it all build in the early
stage.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/mmu.h

@@ -19,6 +19,8 @@ struct mmu_psize_def {
 	unsigned long	sllp;	/* SLB L||LP (exact mask to use in slbmte) */
 };
 extern struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
+
+#define radix_enabled() (0)
 #endif /* __ASSEMBLY__ */
 
 /* 64-bit classic hash table MMU */

arch/powerpc/include/asm/mmu.h

@@ -204,6 +204,9 @@ static inline void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
 #  include <asm/mmu-8xx.h>
 #endif
 
+#ifndef radix_enabled
+#define radix_enabled() (0)
+#endif
 
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_MMU_H_ */

arch/powerpc/platforms/Kconfig.cputype

@@ -331,6 +331,15 @@ config PPC_STD_MMU_64
 	def_bool y
 	depends on PPC_STD_MMU && PPC64
 
+config PPC_RADIX_MMU
+	bool "Radix MMU Support"
+	depends on PPC_BOOK3S_64
+	default y
+	help
+	  Enable support for the Power ISA 3.0 Radix style MMU. Currently this
+	  is only implemented by IBM Power9 CPUs, if you don't have one of them
+	  you can probably disable this.
+
 config PPC_MMU_NOHASH
 	def_bool y
 	depends on !PPC_STD_MMU