powerpc/8xx: Use DAR to save r3 for CPU6 ERRATA

As we are not using anymore DAR to save registers, it is now available for
saving the r3 register used for CPU6 ERRATA handling. Therefore we can
remove the major hack which was to use memory location 0 to save r3.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>

1 files changed, 15 insertions, 18 deletions

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 330d54418494..acf6d7eab6d5 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -83,13 +83,6 @@ _ENTRY(_start);
  * 8M 1:1.  I also mapped an additional I/O space 1:1 so we can get to
  * the "internal" processor registers before MMU_init is called.
  *
- * The TLB code currently contains a major hack.  Since I use the condition
- * code register, I have to save and restore it.  I am out of registers, so
- * I just store it in memory location 0 (the TLB handlers are not reentrant).
- * To avoid making any decisions, I need to use the "segment" valid bit
- * in the first level table, but that would require many changes to the
- * Linux page directory/table functions that I don't want to do right now.
- *
  *      -- Dan
  */
         .globl  __start
@@ -306,7 +299,7 @@ SystemCall:
  */
 InstructionTLBMiss:
 #ifdef CONFIG_8xx_CPU6
-        stw     r3, 8(r0)
+        mtspr   SPRN_DAR, r3
 #endif
         EXCEPTION_PROLOG_0
         mtspr   SPRN_SPRG_SCRATCH2, r10
@@ -351,7 +344,10 @@ InstructionTLBMiss:
 #ifdef CONFIG_SWAP
         andi.   r11, r10, _PAGE_ACCESSED | _PAGE_PRESENT
         cmpwi   cr0, r11, _PAGE_ACCESSED | _PAGE_PRESENT
+        li      r11, RPN_PATTERN
         bne-    cr0, 2f
+#else
+        li      r11, RPN_PATTERN
 #endif
         /* The Linux PTE won't go exactly into the MMU TLB.
          * Software indicator bits 21 and 28 must be clear.
@@ -359,28 +355,29 @@ InstructionTLBMiss:
          * set.  All other Linux PTE bits control the behavior
          * of the MMU.
          */
-        li      r11, RPN_PATTERN
         rlwimi  r10, r11, 0, 0x07f8     /* Set 24-27, clear 21-23,28 */
         MTSPR_CPU6(SPRN_MI_RPN, r10, r3)        /* Update TLB entry */
 
         /* Restore registers */
 #ifdef CONFIG_8xx_CPU6
-        lwz     r3, 8(r0)
+        mfspr   r3, SPRN_DAR
+        mtspr   SPRN_DAR, r11   /* Tag DAR */
 #endif
         mfspr   r10, SPRN_SPRG_SCRATCH2
         EXCEPTION_EPILOG_0
         rfi
 2:
-        mfspr   r11, SPRN_SRR1
+        mfspr   r10, SPRN_SRR1
         /* clear all error bits as TLB Miss
          * sets a few unconditionally
         */
-        rlwinm  r11, r11, 0, 0xffff
-        mtspr   SPRN_SRR1, r11
+        rlwinm  r10, r10, 0, 0xffff
+        mtspr   SPRN_SRR1, r10
 
         /* Restore registers */
 #ifdef CONFIG_8xx_CPU6
-        lwz     r3, 8(r0)
+        mfspr   r3, SPRN_DAR
+        mtspr   SPRN_DAR, r11   /* Tag DAR */
 #endif
         mfspr   r10, SPRN_SPRG_SCRATCH2
         b       InstructionTLBError1
@@ -388,7 +385,7 @@ InstructionTLBMiss:
         . = 0x1200
 DataStoreTLBMiss:
 #ifdef CONFIG_8xx_CPU6
-        stw     r3, 8(r0)
+        mtspr   SPRN_DAR, r3
 #endif
         EXCEPTION_PROLOG_0
         mtspr   SPRN_SPRG_SCRATCH2, r10
@@ -459,7 +456,7 @@ DataStoreTLBMiss:
 
         /* Restore registers */
 #ifdef CONFIG_8xx_CPU6
-        lwz     r3, 8(r0)
+        mfspr   r3, SPRN_DAR
 #endif
         mtspr   SPRN_DAR, r11   /* Tag DAR */
         mfspr   r10, SPRN_SPRG_SCRATCH2
@@ -531,7 +528,7 @@ DARFixed:/* Return from dcbx instruction bug workaround */
 #define NO_SELF_MODIFYING_CODE
 FixupDAR:/* Entry point for dcbx workaround. */
 #ifdef CONFIG_8xx_CPU6
-        stw     r3, 8(r0)
+        mtspr   SPRN_DAR, r3
 #endif
         mtspr   SPRN_SPRG_SCRATCH2, r10
         /* fetch instruction from memory. */
@@ -550,7 +547,7 @@ FixupDAR:/* Entry point for dcbx workaround. */
         rlwinm  r11, r11, 32 - (PAGE_SHIFT - 2), 32 - PAGE_SHIFT, 29
         lwzx    r11, r10, r11   /* Get the pte */
 #ifdef CONFIG_8xx_CPU6
-        lwz     r3, 8(r0)       /* restore r3 from memory */
+        mfspr   r3, SPRN_DAR
 #endif
         /* concat physical page address(r11) and page offset(r10) */
         mfspr   r10, SPRN_SRR0