X-Git-Url: http://git.rot13.org/?a=blobdiff_plain;f=include%2Fasm-sparc64%2Fsystem.h;h=b5417529f6f173dac37d17e900411d9c68ea7929;hb=89a1623df6024e3093f6f3336466809d4f003fe7;hp=ee4bdfc6b88f3a7b047da2361bb117bfbe312581;hpb=2f058256cb64e346f4fb4499ff4e0f1c2791a4b4;p=powerpc.git

diff --git a/include/asm-sparc64/system.h b/include/asm-sparc64/system.h
index ee4bdfc6b8..b5417529f6 100644
--- a/include/asm-sparc64/system.h
+++ b/include/asm-sparc64/system.h
@@ -28,6 +28,49 @@ enum sparc_cpu {
 #define ARCH_SUN4C_SUN4 0
 #define ARCH_SUN4 0
 
+/* These are here in an effort to more fully work around Spitfire Errata
+ * #51.  Essentially, if a memory barrier occurs soon after a mispredicted
+ * branch, the chip can stop executing instructions until a trap occurs.
+ * Therefore, if interrupts are disabled, the chip can hang forever.
+ *
+ * It used to be believed that the memory barrier had to be right in the
+ * delay slot, but a case has been traced recently wherein the memory barrier
+ * was one instruction after the branch delay slot and the chip still hung.
+ * The offending sequence was the following in sym_wakeup_done() of the
+ * sym53c8xx_2 driver:
+ *
+ *	call	sym_ccb_from_dsa, 0
+ *	 movge	%icc, 0, %l0
+ *	brz,pn	%o0, .LL1303
+ *	 mov	%o0, %l2
+ *	membar	#LoadLoad
+ *
+ * The branch has to be mispredicted for the bug to occur.  Therefore, we put
+ * the memory barrier explicitly into a "branch always, predicted taken"
+ * delay slot to avoid the problem case.
+ */
+#define membar_safe(type) \
+do {	__asm__ __volatile__("ba,pt	%%xcc, 1f\n\t" \
+			     " membar	" type "\n" \
+			     "1:\n" \
+			     : : : "memory"); \
+} while (0)
+
+#define mb()	\
+	membar_safe("#LoadLoad | #LoadStore | #StoreStore | #StoreLoad")
+#define rmb()	\
+	membar_safe("#LoadLoad")
+#define wmb()	\
+	membar_safe("#StoreStore")
+#define membar_storeload() \
+	membar_safe("#StoreLoad")
+#define membar_storeload_storestore() \
+	membar_safe("#StoreLoad | #StoreStore")
+#define membar_storeload_loadload() \
+	membar_safe("#StoreLoad | #LoadLoad")
+#define membar_storestore_loadstore() \
+	membar_safe("#StoreStore | #LoadStore")
+
 #endif
 
 #define setipl(__new_ipl) \
@@ -78,16 +121,11 @@ enum sparc_cpu {
 
 #define nop() 		__asm__ __volatile__ ("nop")
 
-#define membar(type)	__asm__ __volatile__ ("membar " type : : : "memory")
-#define mb()		\
-	membar("#LoadLoad | #LoadStore | #StoreStore | #StoreLoad")
-#define rmb()		membar("#LoadLoad")
-#define wmb()		membar("#StoreStore")
 #define read_barrier_depends()		do { } while(0)
 #define set_mb(__var, __value) \
-	do { __var = __value; membar("#StoreLoad | #StoreStore"); } while(0)
+	do { __var = __value; membar_storeload_storestore(); } while(0)
 #define set_wmb(__var, __value) \
-	do { __var = __value; membar("#StoreStore"); } while(0)
+	do { __var = __value; wmb(); } while(0)
 
 #ifdef CONFIG_SMP
 #define smp_mb()	mb()