drm/exynos: fix allocation and cache mapping type

This patch fixes memory alloction(contiguous or not) and
cache mapping types(cachable or not).
For this, it converts each type from user request into dma
attribute properly.

Changelog v2:
- just code cleanup.
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_buf.c

@@ -34,7 +34,7 @@ static int lowlevel_buffer_allocate(struct drm_device *dev,
 		unsigned int flags, struct exynos_drm_gem_buf *buf)
 {
 	int ret = 0;
-	enum dma_attr attr = DMA_ATTR_FORCE_CONTIGUOUS;
+	enum dma_attr attr;
 	unsigned int nr_pages;
 
 	DRM_DEBUG_KMS("%s\n", __FILE__);
@@ -46,8 +46,22 @@ static int lowlevel_buffer_allocate(struct drm_device *dev,
 
 	init_dma_attrs(&buf->dma_attrs);
 
-	if (flags & EXYNOS_BO_NONCONTIG)
+	/*
+	 * if EXYNOS_BO_CONTIG, fully physically contiguous memory
+	 * region will be allocated else physically contiguous
+	 * as possible.
+	 */
+	if (flags & EXYNOS_BO_CONTIG)
+		dma_set_attr(DMA_ATTR_FORCE_CONTIGUOUS, &buf->dma_attrs);
+
+	/*
+	 * if EXYNOS_BO_WC or EXYNOS_BO_NONCACHABLE, writecombine mapping
+	 * else cachable mapping.
+	 */
+	if (flags & EXYNOS_BO_WC || !(flags & EXYNOS_BO_CACHABLE))
 		attr = DMA_ATTR_WRITE_COMBINE;
+	else
+		attr = DMA_ATTR_NON_CONSISTENT;
 
 	dma_set_attr(attr, &buf->dma_attrs);
 	dma_set_attr(DMA_ATTR_NO_KERNEL_MAPPING, &buf->dma_attrs);