powerpc/476: Workaround for PLB6 hang

The 476FP core may hang if an instruction fetch happens during an msync
following a tlbsync.  This workaround makes sure that enough instruction
cache lines are pre-fetched before executing the msync.  (sync and msync
are the same to the compiler.)
Signed-off-by: NDave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/mm/tlb_nohash_low.S

@@ -189,6 +189,13 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_47x)
 	blr
 
 #ifdef CONFIG_PPC_47x
+
+/*
+ * 47x variant of icbt
+ */
+# define ICBT(CT,RA,RB)	\
+	.long	0x7c00002c | ((CT) << 21) | ((RA) << 16) | ((RB) << 11)
+
 /*
  * _tlbivax_bcast is only on 47x. We don't bother doing a runtime
  * check though, it will blow up soon enough if we mistakenly try
@@ -206,7 +213,35 @@ _GLOBAL(_tlbivax_bcast)
 	isync
 	eieio
 	tlbsync
+BEGIN_FTR_SECTION
+	b	1f
+END_FTR_SECTION_IFSET(CPU_FTR_476_DD2)
+	sync
+	wrtee	r10
+	blr
+/*
+ * DD2 HW could hang if in instruction fetch happens before msync completes.
+ * Touch enough instruction cache lines to ensure cache hits
+ */
+1:	mflr	r9
+	bl	2f
+2:	mflr	r6
+	li	r7,32
+	ICBT(0,r6,r7)		/* touch next cache line */
+	add	r6,r6,r7
+	ICBT(0,r6,r7)		/* touch next cache line */
+	add	r6,r6,r7
+	ICBT(0,r6,r7)		/* touch next cache line */
 	sync
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	mtlr	r9
 	wrtee	r10
 	blr
 #endif /* CONFIG_PPC_47x */