powerpc/e6500: Make TLB lock recursive

Once special level interrupts are supported, we may take nested TLB
misses -- so allow the same thread to acquire the lock recursively.

The lock will not be effective against the nested TLB miss handler
trying to write the same entry as the interrupted TLB miss handler, but
that's also a problem on non-threaded CPUs that lack TLB write
conditional.  This will be addressed in the patch that enables crit/mc
support by invalidating the TLB on return from level exceptions.

Signed-off-by: Scott Wood <scottwood@freescale.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/arch/powerpc/mm/tlb_low_64e.S b/arch/powerpc/mm/tlb_low_64e.S
index 6bf50507a4b5..1e50249e900b 100644
--- a/arch/powerpc/mm/tlb_low_64e.S
+++ b/arch/powerpc/mm/tlb_low_64e.S
@@ -284,7 +284,7 @@ itlb_miss_fault_bolted:
  * r14 = page table base
  * r13 = PACA
  * r11 = tlb_per_core ptr
- * r10 = crap (free to use)
+ * r10 = cpu number
  */
 tlb_miss_common_e6500:
         /*
@@ -293,15 +293,18 @@ tlb_miss_common_e6500:
          *
          * MAS6:IND should be already set based on MAS4
          */
-        addi    r10,r11,TCD_LOCK
-1:      lbarx   r15,0,r10
+1:      lbarx   r15,0,r11
+        lhz     r10,PACAPACAINDEX(r13)
         cmpdi   r15,0
+        cmpdi   cr1,r15,1       /* set cr1.eq = 0 for non-recursive */
         bne     2f
-        li      r15,1
-        stbcx.  r15,0,r10
+        stbcx.  r10,0,r11
         bne     1b
+3:
         .subsection 1
-2:      lbz     r15,0(r10)
+2:      cmpd    cr1,r15,r10     /* recursive lock due to mcheck/crit/etc? */
+        beq     cr1,3b          /* unlock will happen if cr1.eq = 0 */
+        lbz     r15,0(r11)
         cmpdi   r15,0
         bne     2b
         b       1b
@@ -379,9 +382,11 @@ tlb_miss_common_e6500:
 
 tlb_miss_done_e6500:
         .macro  tlb_unlock_e6500
+        beq     cr1,1f          /* no unlock if lock was recursively grabbed */
         li      r15,0
         isync
-        stb     r15,TCD_LOCK(r11)
+        stb     r15,0(r11)
+1:
         .endm
 
         tlb_unlock_e6500