powerpc/mm/radix: Add MMU_FTR_RADIX

We are going to add asm changes in the follow up patches. Add the
feature bit now so that we can get it all build.

mpe: When CONFIG_PPC_RADIX_MMU=n we omit MMU_FTR_RADIX from the
MMU_FTRS_POSSIBLE mask. This allows the compiler to work out that those
checks will always be false and so the code can be elided completely.

Note we do *not* define MMU_FTR_RADIX to 0 in the RADIX_MMU=n case,
because that doesn't work with the ASM_FTR patching. In particular an
IF_SET section will result in a mask and value of zero, which is always
true, meaning the section *won't* be patched, which is the opposite of
what we want.

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

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

@@ -23,7 +23,8 @@ struct mmu_psize_def {
 };
 extern struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
 
-#define radix_enabled() (0)
+#define radix_enabled() mmu_has_feature(MMU_FTR_RADIX)
+
 #endif /* __ASSEMBLY__ */
 
 /* 64-bit classic hash table MMU */

arch/powerpc/include/asm/mmu.h

@@ -88,6 +88,11 @@
  */
 #define MMU_FTR_1T_SEGMENT		ASM_CONST(0x40000000)
 
+/*
+ * Radix page table available
+ */
+#define MMU_FTR_RADIX			ASM_CONST(0x80000000)
+
 /* MMU feature bit sets for various CPUs */
 #define MMU_FTRS_DEFAULT_HPTE_ARCH_V2	\
 	MMU_FTR_HPTE_TABLE | MMU_FTR_PPCAS_ARCH_V2
@@ -119,7 +124,11 @@ enum {
 		MMU_FTR_USE_TLBRSRV | MMU_FTR_USE_PAIRED_MAS |
 		MMU_FTR_NO_SLBIE_B | MMU_FTR_16M_PAGE | MMU_FTR_TLBIEL |
 		MMU_FTR_LOCKLESS_TLBIE | MMU_FTR_CI_LARGE_PAGE |
-		MMU_FTR_1T_SEGMENT,
+		MMU_FTR_1T_SEGMENT |
+#ifdef CONFIG_PPC_RADIX_MMU
+		MMU_FTR_RADIX |
+#endif
+		0,
 };
 
 static inline int mmu_has_feature(unsigned long feature)