MN10300: AM34 erratum requires MMUCTR read and write on exception entry

An AM34 erratum requires MMUCTR read and write on entry to certain exceptions,
prior to EPSW.NMID being cleared to allow NMIs to happen.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>

arch/mn10300/Kconfig

@@ -20,6 +20,9 @@ config AM34_2
 	select MN10300_HAS_ATOMIC_OPS_UNIT
 	select MN10300_HAS_CACHE_SNOOP
 
+config ERRATUM_NEED_TO_RELOAD_MMUCTR
+	def_bool y if AM33_3 || AM34_2
+
 config MMU
 	def_bool y
 

arch/mn10300/kernel/entry.S

@@ -251,6 +251,10 @@ double_fault_loop:
 ENTRY(raw_bus_error)
 	add	-4,sp
 	mov	d0,(sp)
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d0
+	mov	d0,(MMUCTR)
+#endif
 	mov	(BCBERR),d0		# what
 	btst	BCBERR_BEMR_DMA,d0	# see if it was an external bus error
 	beq	__common_exception_aux	# it wasn't
@@ -282,6 +286,10 @@ ENTRY(nmi_handler)
 ENTRY(__common_exception)
 	add	-4,sp
 	mov	d0,(sp)
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d0
+	mov	d0,(MMUCTR)
+#endif
 
 __common_exception_aux:
 	mov	(TBR),d0

arch/mn10300/mm/tlb-mn10300.S

@@ -27,7 +27,6 @@
 ###############################################################################
 	.type	itlb_miss,@function
 ENTRY(itlb_miss)
-	and	~EPSW_NMID,epsw
 #ifdef CONFIG_GDBSTUB
 	movm	[d2,d3,a2],(sp)
 #else
@@ -38,6 +37,12 @@ ENTRY(itlb_miss)
 	nop
 #endif
 
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d2
+	mov	d2,(MMUCTR)
+#endif
+
+	and	~EPSW_NMID,epsw
 	mov	(IPTEU),d3
 	mov	(PTBR),a2
 	mov	d3,d2
@@ -79,7 +84,6 @@ itlb_miss_fault:
 ###############################################################################
 	.type	dtlb_miss,@function
 ENTRY(dtlb_miss)
-	and	~EPSW_NMID,epsw
 #ifdef CONFIG_GDBSTUB
 	movm	[d2,d3,a2],(sp)
 #else
@@ -90,6 +94,12 @@ ENTRY(dtlb_miss)
 	nop
 #endif
 
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d2
+	mov	d2,(MMUCTR)
+#endif
+
+	and	~EPSW_NMID,epsw
 	mov	(DPTEU),d3
 	mov	(PTBR),a2
 	mov	d3,d2
@@ -130,9 +140,15 @@ dtlb_miss_fault:
 ###############################################################################
 	.type	itlb_aerror,@function
 ENTRY(itlb_aerror)
-	and	~EPSW_NMID,epsw
 	add	-4,sp
 	SAVE_ALL
+
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d1
+	mov	d1,(MMUCTR)
+#endif
+
+	and	~EPSW_NMID,epsw
 	add	-4,sp				# need to pass three params
 
 	# calculate the fault code
@@ -148,7 +164,6 @@ ENTRY(itlb_aerror)
 	clr	d0
 	mov	d0,(IPTEL)
 
-	and	~EPSW_NMID,epsw
 	or	EPSW_IE,epsw
 	mov	fp,d0
 	call	do_page_fault[],0		# do_page_fault(regs,code,addr
@@ -163,10 +178,16 @@ ENTRY(itlb_aerror)
 ###############################################################################
 	.type	dtlb_aerror,@function
 ENTRY(dtlb_aerror)
-	and	~EPSW_NMID,epsw
 	add	-4,sp
 	SAVE_ALL
+
+#if defined(CONFIG_ERRATUM_NEED_TO_RELOAD_MMUCTR)
+	mov	(MMUCTR),d1
+	mov	d1,(MMUCTR)
+#endif
+
 	add	-4,sp				# need to pass three params
+	and	~EPSW_NMID,epsw
 
 	# calculate the fault code
 	movhu	(MMUFCR_DFC),d1
@@ -180,7 +201,6 @@ ENTRY(dtlb_aerror)
 	clr	d0
 	mov	d0,(DPTEL)
 
-	and	~EPSW_NMID,epsw
 	or	EPSW_IE,epsw
 	mov	fp,d0
 	call	do_page_fault[],0		# do_page_fault(regs,code,addr