[PATCH] EDAC: atomic scrub operations

EDAC requires a way to scrub memory if an ECC error is found and the chipset
does not do the work automatically.  That means rewriting memory locations
atomically with respect to all CPUs _and_ bus masters.  That means we can't
use atomic_add(foo, 0) as it gets optimised for non-SMP

This adds a function to include/asm-foo/atomic.h for the platforms currently
supported which implements a scrub of a mapped block.

It also adjusts a few other files include order where atomic.h is included
before types.h as this now causes an error as atomic_scrub uses u32.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 24 insertions, 0 deletions

diff --git a/include/asm-i386/atomic.h b/include/asm-i386/atomic.h
index de649d3aa2d4..e2c00c95a5e1 100644
--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -255,5 +255,17 @@ __asm__ __volatile__(LOCK "orl %0,%1" \
 #define smp_mb__before_atomic_inc()     barrier()
 #define smp_mb__after_atomic_inc()      barrier()
 
+/* ECC atomic, DMA, SMP and interrupt safe scrub function */
+
+static __inline__ void atomic_scrub(unsigned long *virt_addr, u32 size)
+{
+        u32 i;
+        for (i = 0; i < size / 4; i++, virt_addr++)
+                /* Very carefully read and write to memory atomically
+                 * so we are interrupt, DMA and SMP safe.
+                 */
+                __asm__ __volatile__("lock; addl $0, %0"::"m"(*virt_addr));
+}
+
 #include <asm-generic/atomic.h>
 #endif
diff --git a/include/asm-x86_64/atomic.h b/include/asm-x86_64/atomic.h
index 4b5cd553e772..4048508c4f40 100644
--- a/include/asm-x86_64/atomic.h
+++ b/include/asm-x86_64/atomic.h
@@ -426,5 +426,17 @@ __asm__ __volatile__(LOCK "orl %0,%1" \
 #define smp_mb__before_atomic_inc()     barrier()
 #define smp_mb__after_atomic_inc()      barrier()
 
+/* ECC atomic, DMA, SMP and interrupt safe scrub function */
+
+static __inline__ void atomic_scrub(u32 *virt_addr, u32 size)
+{
+        u32 i;
+        for (i = 0; i < size / 4; i++, virt_addr++)
+                /* Very carefully read and write to memory atomically
+                 * so we are interrupt, DMA and SMP safe.
+                 */
+                __asm__ __volatile__("lock; addl $0, %0"::"m"(*virt_addr));
+}
+
 #include <asm-generic/atomic.h>
 #endif