openrisc: head: Init r0 to 0 on start

Originally openrisc spec 0 specified that r0 would be wired to ground.
This is no longer the case.  r0 is not guaranteed to be 0 at init, so we
need to initialize it to 0 before using it.

Also, if we are clearing r0 we cant use r0 to clear itself. Change the
the CLEAR_GPR macro to use movhi for clearing.

Reported-by: Jakob Viketoft <jakob.viketoft@aacmicrotec.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index fe55156983e0..d01b82eace3e 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -35,7 +35,7 @@
         l.add   rd,rd,rs
 
 #define CLEAR_GPR(gpr)                          \
-        l.or    gpr,r0,r0
+        l.movhi gpr,0x0
 
 #define LOAD_SYMBOL_2_GPR(gpr,symbol)           \
         l.movhi gpr,hi(symbol)                  ;\
@@ -443,6 +443,9 @@ _dispatch_do_ipage_fault:
         __HEAD
         .global _start
 _start:
+        /* Init r0 to zero as per spec */
+        CLEAR_GPR(r0)
+
         /* save kernel parameters */
         l.or    r25,r0,r3       /* pointer to fdt */