include/asm-:mips add missing edac h file

EDAC has a foundation to perform software memory scrubbing, but it requires a
per architecture (atomic_scrub) function for performing an atomic update
operation.  Under X86, this is done with a

lock:  add  [addr],0

in the file asm-x86/edac.h

This patch provides the MIPS arch with that atomic function, atomic_scrub() in

asm-mips/edac.h

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: NDoug Thompson <dougthompson@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/asm-mips/edac.h

+#ifndef ASM_EDAC_H
+#define ASM_EDAC_H
+
+/* ECC atomic, DMA, SMP and interrupt safe scrub function */
+
+static inline void atomic_scrub(void *va, u32 size)
+{
+	unsigned long *virt_addr = va;
+	unsigned long temp;
+	u32 i;
+
+	for (i = 0; i < size / sizeof(unsigned long); i++, virt_addr++) {
+
+		/*
+		 * Very carefully read and write to memory atomically
+		 * so we are interrupt, DMA and SMP safe.
+		 *
+		 * Intel: asm("lock; addl $0, %0"::"m"(*virt_addr));
+		 */
+
+		__asm__ __volatile__ (
+		"       .set    mips3                                   \n"
+		"1:     ll      %0, %1          # atomic_add            \n"
+		"       ll      %0, %1          # atomic_add            \n"
+		"       addu    %0, $0                                  \n"
+		"       sc      %0, %1                                  \n"
+		"       beqz    %0, 1b                                  \n"
+		"       .set    mips0                                   \n"
+		: "=&r" (temp), "=m" (*virt_addr)
+		: "m" (*virt_addr));
+
+	}
+}
+
+#endif