drivers: dma-coherent: use MEMREMAP_WC for DMA_MEMORY_MAP

When the DMA_MEMORY_MAP flag is used, memory which can be accessed
directly should be returned, so use memremap(..., MEMREMAP_WC) to
provide a writecombine mapping.

Signed-off-by: Brian Starkey <[e-mail]>
Reviewed-by: Catalin Marinas <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/dma-coherent.c

···
  * Coherent per-device memory handling.
  * Borrowed from i386
  */
+#include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
···
 	if (!size)
 		goto out;
 
-	mem_base = ioremap(phys_addr, size);
+	if (flags & DMA_MEMORY_MAP)
+		mem_base = memremap(phys_addr, size, MEMREMAP_WC);
+	else
+		mem_base = ioremap(phys_addr, size);
 	if (!mem_base)
 		goto out;
 
···
 
 out:
 	kfree(dma_mem);
-	if (mem_base)
-		iounmap(mem_base);
+	if (mem_base) {
+		if (flags & DMA_MEMORY_MAP)
+			memunmap(mem_base);
+		else
+			iounmap(mem_base);
+	}
 	return false;
 }
 
···
 {
 	if (!mem)
 		return;
-	iounmap(mem->virt_base);
+
+	if (mem->flags & DMA_MEMORY_MAP)
+		memunmap(mem->virt_base);
+	else
+		iounmap(mem->virt_base);
 	kfree(mem->bitmap);
 	kfree(mem);
 }