1 files changed, 34 insertions, 9 deletions

diff --git a/include/asm-sh/system.h b/include/asm-sh/system.h
index eb4902ed920a..1630a5411e5f 100644
--- a/include/asm-sh/system.h
+++ b/include/asm-sh/system.h
@@ -67,8 +67,17 @@ static inline void sched_cacheflush(void)
 {
 }
 
-#define nop() __asm__ __volatile__ ("nop")
-
+#ifdef CONFIG_CPU_SH4A
+#define __icbi()                        \
+{                                       \
+        unsigned long __addr;           \
+        __addr = 0xa8000000;            \
+        __asm__ __volatile__(           \
+                "icbi   %0\n\t"         \
+                : /* no output */       \
+                : "m" (__m(__addr)));   \
+}
+#endif
 
 #define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
 
@@ -84,15 +93,31 @@ static __inline__ unsigned long tas(volatile int *m)
 
 extern void __xchg_called_with_bad_pointer(void);
 
+/*
+ * A brief note on ctrl_barrier(), the control register write barrier.
+ *
+ * Legacy SH cores typically require a sequence of 8 nops after
+ * modification of a control register in order for the changes to take
+ * effect. On newer cores (like the sh4a and sh5) this is accomplished
+ * with icbi.
+ *
+ * Also note that on sh4a in the icbi case we can forego a synco for the
+ * write barrier, as it's not necessary for control registers.
+ *
+ * Historically we have only done this type of barrier for the MMUCR, but
+ * it's also necessary for the CCR, so we make it generic here instead.
+ */
 #ifdef CONFIG_CPU_SH4A
-#define mb()    __asm__ __volatile__ ("synco": : :"memory")
-#define rmb()   mb()
-#define wmb()   __asm__ __volatile__ ("synco": : :"memory")
+#define mb()            __asm__ __volatile__ ("synco": : :"memory")
+#define rmb()           mb()
+#define wmb()           __asm__ __volatile__ ("synco": : :"memory")
+#define ctrl_barrier()  __icbi()
 #define read_barrier_depends()  do { } while(0)
 #else
-#define mb()    __asm__ __volatile__ ("": : :"memory")
-#define rmb()   mb()
-#define wmb()   __asm__ __volatile__ ("": : :"memory")
+#define mb()            __asm__ __volatile__ ("": : :"memory")
+#define rmb()           mb()
+#define wmb()           __asm__ __volatile__ ("": : :"memory")
+#define ctrl_barrier()  __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop")
 #define read_barrier_depends()  do { } while(0)
 #endif
 
@@ -218,8 +243,8 @@ do {					\
 #define back_to_P1()                                    \
 do {                                                    \
         unsigned long __dummy;                          \
+        ctrl_barrier();                                 \
         __asm__ __volatile__(                           \
-                "nop;nop;nop;nop;nop;nop;nop\n\t"       \
                 "mov.l  1f, %0\n\t"                     \
                 "jmp    @%0\n\t"                        \
                 " nop\n\t"                              \