powerpc/4xx: Extended DCR support v2

This adds supports to the "extended" DCR addressing via the indirect
mfdcrx/mtdcrx instructions supported by some 4xx cores (440H6 and
later).

I enabled the feature for now only on AMCC 460 chips.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/powerpc/sysdev/dcr-low.S b/arch/powerpc/sysdev/dcr-low.S
index 2078f39e2f17..d3098ef1404a 100644
--- a/arch/powerpc/sysdev/dcr-low.S
+++ b/arch/powerpc/sysdev/dcr-low.S
@@ -11,14 +11,20 @@
 
 #include <asm/ppc_asm.h>
 #include <asm/processor.h>
+#include <asm/bug.h>
 
 #define DCR_ACCESS_PROLOG(table) \
+        cmpli   cr0,r3,1024;     \
         rlwinm  r3,r3,4,18,27;   \
         lis     r5,table@h;      \
         ori     r5,r5,table@l;   \
         add     r3,r3,r5;        \
+        bge-    1f;              \
         mtctr   r3;              \
-        bctr
+        bctr;                    \
+1:      trap;                    \
+        EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,0;  \
+        blr
 
 _GLOBAL(__mfdcr)
         DCR_ACCESS_PROLOG(__mfdcr_table)