---
 arch/x86_64/mm/ioremap.c |   45 ++++++++++++++++++++++++++++++++++++---------
 include/asm-x86_64/io.h  |    3 ++-
 2 files changed, 38 insertions(+), 10 deletions(-)

Index: linux/arch/x86_64/mm/ioremap.c
===================================================================
--- linux.orig/arch/x86_64/mm/ioremap.c
+++ linux/arch/x86_64/mm/ioremap.c
@@ -214,14 +214,17 @@ void __iomem * __ioremap(unsigned long p
 		remove_vm_area((void *)(PAGE_MASK & (unsigned long) addr));
 		return NULL;
 	}
-	if (flags) {
-		if (reserve_mattr(phys_addr, phys_addr + size, flags, NULL) < 0)
-			goto out;
-	     	if (ioremap_change_attr(phys_addr, size, flags) < 0) {
-			free_mattr(phys_addr, phys_addr + size, flags);
-			goto out;
-		}	
-	}
+
+	/* For plain ioremap() get the existing attributes. Otherwise
+  	   check against the existing ones */
+	if (reserve_mattr(phys_addr, phys_addr + size, flags,
+			  flags ? NULL : &flags) < 0)
+		goto out;
+
+     	if (flags && ioremap_change_attr(phys_addr, size, flags) < 0) {
+		free_mattr(phys_addr, phys_addr + size, flags);
+		goto out;
+	}
 	return (__force void __iomem *) (offset + (char *)addr);
 
 out:
@@ -232,7 +235,7 @@ out:
 EXPORT_SYMBOL(__ioremap);
 
 /**
- * ioremap_nocache     -   map bus memory into CPU space
+ * ioremap_nocache     -   map bus memory into CPU space uncached
  * @offset:    bus address of the memory
  * @size:      size of the resource to map
  *
@@ -260,6 +263,30 @@ void __iomem *ioremap_nocache (unsigned 
 EXPORT_SYMBOL(ioremap_nocache);
 
 /**
+ * ioremap_wc    -   map bus memory into CPU space write combined
+ * @offset:    bus address of the memory
+ * @size:      size of the resource to map
+ *
+ * ioremap_wc performs a platform specific sequence of operations to
+ * make bus memory CPU accessible via the readb/readw/readl/writeb/
+ * writew/writel functions and the other mmio helpers. The returned
+ * address is not guaranteed to be usable directly as a virtual
+ * address.
+ *
+ * This version of ioremap ensures that the memory is marked write combining.
+ * Write combining allows faster writes to some hardware devices.
+ * See also iounmap_nocache for more details.
+ *
+ * Must be freed with iounmap.
+ */
+void __iomem *ioremap_wc(unsigned long phys_addr, unsigned long size)
+{
+	return __ioremap(phys_addr, size, _PAGE_WC);
+}
+EXPORT_SYMBOL(ioremap_wc);
+
+
+/**
  * iounmap - Free a IO remapping
  * @addr: virtual address from ioremap_*
  *
Index: linux/include/asm-x86_64/io.h
===================================================================
--- linux.orig/include/asm-x86_64/io.h
+++ linux/include/asm-x86_64/io.h
@@ -142,7 +142,8 @@ extern void early_iounmap(void *addr, un
  * it's useful if some control registers are in such an area and write combining
  * or read caching is not desirable:
  */
-extern void __iomem * ioremap_nocache (unsigned long offset, unsigned long size);
+extern void __iomem * ioremap_nocache(unsigned long offset, unsigned long size);
+extern void __iomem * ioremap_wc(unsigned long offset, unsigned long size);
 extern void iounmap(volatile void __iomem *addr);
 
 /*