[POWERPC] EDAC ECC software scrubber

Implements the per arch atomic_scrub() that EDAC uses for software
ECC scrubbing.  It reads memory and then writes back the original
value, allowing the hardware to detect and correct memory errors.
Signed-off-by: Dave Jiang <djiang@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/edac.h

+/*
+ * PPC EDAC common defs
+ *
+ * Author: Dave Jiang <djiang@mvista.com>
+ *
+ * 2007 (c) MontaVista Software, Inc. This file is licensed under
+ * the terms of the GNU General Public License version 2. This program
+ * is licensed "as is" without any warranty of any kind, whether express
+ * or implied.
+ */
+#ifndef ASM_EDAC_H
+#define ASM_EDAC_H
+/*
+ * ECC atomic, DMA, SMP and interrupt safe scrub function.
+ * Implements the per arch atomic_scrub() that EDAC use for software
+ * ECC scrubbing.  It reads memory and then writes back the original
+ * value, allowing the hardware to detect and correct memory errors.
+ */
+static __inline__ void atomic_scrub(void *va, u32 size)
+{
+	unsigned int *virt_addr = va;
+	unsigned int temp;
+	unsigned int i;
+
+	for (i = 0; i < size / sizeof(*virt_addr); i++, virt_addr++) {
+		/* Very carefully read and write to memory atomically
+		 * so we are interrupt, DMA and SMP safe.
+		 */
+		__asm__ __volatile__ ("\n\
+				1:	lwarx	%0,0,%1\n\
+					stwcx.	%0,0,%1\n\
+					bne-	1b\n\
+					isync"
+					: "=&r"(temp)
+					: "r"(virt_addr)
+					: "cr0", "memory");
+	}
+}
+
+#endif