[PATCH RFC 4/4] powerpc/radix: Add support for microwatt's PRTBL SPR

[Paul Mackerras <paulus@ozlabs.org>]

Microwatt currently doesn't implement hypervisor mode and therefore
doesn't implement the partition table.  It does implement the process
table and radix page table walks.

This adds code to write the base address of the process table to the
PRTBL SPR, which has been assigned SPR 720 for now, as that is in the
range of SPR numbers assigned for experimental use.  PRTBL is only
written when we have neither the FW_FEATURE_LPAR feature nor the
CPU_FTR_HVMODE feature.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
 arch/powerpc/include/asm/reg.h           |  1 +
 arch/powerpc/mm/book3s64/radix_pgtable.c | 13 +++++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1aa46dff0957..6ea3fc42740d 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -721,6 +721,7 @@
 #endif
 #define SPRN_TIR	0x1BE	/* Thread Identification Register */
 #define SPRN_PTCR	0x1D0	/* Partition table control Register */
+#define SPRN_PRTBL	0x2D0	/* Process table pointer */
 #define SPRN_PSPB	0x09F	/* Problem State Priority Boost reg */
 #define SPRN_PTEHI	0x3D5	/* 981 7450 PTE HI word (S/W TLB load) */
 #define SPRN_PTELO	0x3D6	/* 982 7450 PTE LO word (S/W TLB load) */
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index dd1bea45325c..2e6a376c9d82 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -600,10 +600,15 @@ void __init radix__early_init_mmu(void)
 	radix_init_pgtable();
 
 	if (!firmware_has_feature(FW_FEATURE_LPAR)) {
-		lpcr = mfspr(SPRN_LPCR);
-		mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
-		radix_init_partition_table();
-		radix_init_amor();
+		if (cpu_has_feature(CPU_FTR_HVMODE)) {
+			lpcr = mfspr(SPRN_LPCR);
+			mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
+			radix_init_partition_table();
+			radix_init_amor();
+		} else {
+			mtspr(SPRN_PRTBL, (__pa(process_tb) |
+					   (PRTB_SIZE_SHIFT - 12)));
+		}
 	} else {
 		radix_init_pseries();
 	}
-- 
2.25.3