[PATCH v1 4/6] powerpc/8xx: Use SPRN_SPRG_SCRATCH2 in ITLB miss exception

[Christophe Leroy]

In order to re-enable MMU earlier, ensure ITLB miss exception
cannot clobber SPRN_SPRG_SCRATCH0 and SPRN_SPRG_SCRATCH1.
Do so by using SPRN_SPRG_SCRATCH2 and SPRN_M_TW instead, like
the DTLB miss exception.

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 arch/powerpc/kernel/head_8xx.S | 12 ++++++------
 arch/powerpc/perf/8xx-pmu.c    |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 558c8e615ef9..45239b06b6ce 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -190,8 +190,8 @@ SystemCall:
 #endif
 
 InstructionTLBMiss:
-       mtspr   SPRN_SPRG_SCRATCH0, r10
-       mtspr   SPRN_SPRG_SCRATCH1, r11
+       mtspr   SPRN_SPRG_SCRATCH2, r10
+       mtspr   SPRN_M_TW, r11
 
        /* If we are faulting a kernel address, we have to use the
         * kernel page tables.
@@ -230,8 +230,8 @@ InstructionTLBMiss:
        mtspr   SPRN_MI_RPN, r10        /* Update TLB entry */
 
        /* Restore registers */
-0:     mfspr   r10, SPRN_SPRG_SCRATCH0
-       mfspr   r11, SPRN_SPRG_SCRATCH1
+0:     mfspr   r10, SPRN_SPRG_SCRATCH2
+       mfspr   r11, SPRN_M_TW
        rfi
        patch_site      0b, patch__itlbmiss_exit_1
 
@@ -240,8 +240,8 @@ InstructionTLBMiss:
 0:     lwz     r10, (itlb_miss_counter - PAGE_OFFSET)@l(0)
        addi    r10, r10, 1
        stw     r10, (itlb_miss_counter - PAGE_OFFSET)@l(0)
-       mfspr   r10, SPRN_SPRG_SCRATCH0
-       mfspr   r11, SPRN_SPRG_SCRATCH1
+       mfspr   r10, SPRN_SPRG_SCRATCH2
+       mfspr   r11, SPRN_M_TW
        rfi
 #endif
 
diff --git a/arch/powerpc/perf/8xx-pmu.c b/arch/powerpc/perf/8xx-pmu.c
index e53c3c161257..02db58c7427a 100644
--- a/arch/powerpc/perf/8xx-pmu.c
+++ b/arch/powerpc/perf/8xx-pmu.c
@@ -165,9 +165,9 @@ static void mpc8xx_pmu_del(struct perf_event *event, int 
flags)
                break;
        case PERF_8xx_ID_ITLB_LOAD_MISS:
                if (atomic_dec_return(&itlb_miss_ref) == 0) {
-                       /* mfspr r10, SPRN_SPRG_SCRATCH0 */
+                       /* mfspr r10, SPRN_SPRG_SCRATCH2 */
                        struct ppc_inst insn = ppc_inst(PPC_INST_MFSPR | 
__PPC_RS(R10) |
-                                           __PPC_SPR(SPRN_SPRG_SCRATCH0));
+                                           __PPC_SPR(SPRN_SPRG_SCRATCH2));
 
                        patch_instruction_site(&patch__itlbmiss_exit_1, insn);
                }
-- 
2.25.0