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 <brian.starkey@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/dma-coherent.c

@@ -2,6 +2,7 @@
  * Coherent per-device memory handling.
  * Borrowed from i386
  */
+#include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -31,6 +32,9 @@ static bool dma_init_coherent_memory(
 	if (!size)
 		goto out;
 
+	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;
@@ -54,8 +58,12 @@ static bool dma_init_coherent_memory(
 
 out:
 	kfree(dma_mem);
-	if (mem_base)
+	if (mem_base) {
+		if (flags & DMA_MEMORY_MAP)
+			memunmap(mem_base);
+		else
 			iounmap(mem_base);
+	}
 	return false;
 }
 
@@ -63,6 +71,10 @@ static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
 {
 	if (!mem)
 		return;
+
+	if (mem->flags & DMA_MEMORY_MAP)
+		memunmap(mem->virt_base);
+	else
 		iounmap(mem->virt_base);
 	kfree(mem->bitmap);
 	kfree(mem);