drm/exynos/gem: remove DMA-mapping hacks used for constructing page array

Exynos GEM objects contains an array of pointers to the pages, which the
allocated buffer consists of. Till now the code used some hacks (like
relying on DMA-mapping internal structures or using ARM-specific
dma_to_pfn helper) to build this array. This patch fixes this by adding
proper call to dma_get_sgtable_attrs() and using the acquired scatter-list
to construct needed array. This approach is more portable (work also for
ARM64) and finally fixes the layering violation that was present in this
code.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_gem.c

@@ -25,6 +25,8 @@ static int exynos_drm_alloc_buf(struct exynos_drm_gem *exynos_gem)
 	struct drm_device *dev = exynos_gem->base.dev;
 	enum dma_attr attr;
 	unsigned int nr_pages;
+	struct sg_table sgt;
+	int ret = -ENOMEM;
 
 	if (exynos_gem->dma_addr) {
 		DRM_DEBUG_KMS("already allocated.\n");
@@ -56,13 +58,10 @@ static int exynos_drm_alloc_buf(struct exynos_drm_gem *exynos_gem)
 
 	nr_pages = exynos_gem->size >> PAGE_SHIFT;
 
-	if (!is_drm_iommu_supported(dev)) {
-		exynos_gem->pages = drm_calloc_large(nr_pages,
-						     sizeof(struct page *));
-		if (!exynos_gem->pages) {
-			DRM_ERROR("failed to allocate pages.\n");
-			return -ENOMEM;
-		}
+	exynos_gem->pages = drm_calloc_large(nr_pages, sizeof(struct page *));
+	if (!exynos_gem->pages) {
+		DRM_ERROR("failed to allocate pages.\n");
+		return -ENOMEM;
 	}
 
 	exynos_gem->cookie = dma_alloc_attrs(dev->dev, exynos_gem->size,
@@ -70,30 +69,40 @@ static int exynos_drm_alloc_buf(struct exynos_drm_gem *exynos_gem)
 					     &exynos_gem->dma_attrs);
 	if (!exynos_gem->cookie) {
 		DRM_ERROR("failed to allocate buffer.\n");
-		if (exynos_gem->pages)
-			drm_free_large(exynos_gem->pages);
-		return -ENOMEM;
+		goto err_free;
 	}
 
-	if (exynos_gem->pages) {
-		dma_addr_t start_addr;
-		unsigned int i = 0;
-
-		start_addr = exynos_gem->dma_addr;
-		while (i < nr_pages) {
-			exynos_gem->pages[i] =
-				pfn_to_page(dma_to_pfn(dev->dev, start_addr));
-			start_addr += PAGE_SIZE;
-			i++;
-		}
-	} else {
-		exynos_gem->pages = exynos_gem->cookie;
+	ret = dma_get_sgtable_attrs(dev->dev, &sgt, exynos_gem->cookie,
+				    exynos_gem->dma_addr, exynos_gem->size,
+				    &exynos_gem->dma_attrs);
+	if (ret < 0) {
+		DRM_ERROR("failed to get sgtable.\n");
+		goto err_dma_free;
+	}
+
+	if (drm_prime_sg_to_page_addr_arrays(&sgt, exynos_gem->pages, NULL,
+					     nr_pages)) {
+		DRM_ERROR("invalid sgtable.\n");
+		ret = -EINVAL;
+		goto err_sgt_free;
 	}
 
+	sg_free_table(&sgt);
+
 	DRM_DEBUG_KMS("dma_addr(0x%lx), size(0x%lx)\n",
 			(unsigned long)exynos_gem->dma_addr, exynos_gem->size);
 
 	return 0;
+
+err_sgt_free:
+	sg_free_table(&sgt);
+err_dma_free:
+	dma_free_attrs(dev->dev, exynos_gem->size, exynos_gem->cookie,
+		       exynos_gem->dma_addr, &exynos_gem->dma_attrs);
+err_free:
+	drm_free_large(exynos_gem->pages);
+
+	return ret;
 }
 
 static void exynos_drm_free_buf(struct exynos_drm_gem *exynos_gem)
@@ -112,8 +121,7 @@ static void exynos_drm_free_buf(struct exynos_drm_gem *exynos_gem)
 			(dma_addr_t)exynos_gem->dma_addr,
 			&exynos_gem->dma_attrs);
 
-	if (!is_drm_iommu_supported(dev))
-		drm_free_large(exynos_gem->pages);
+	drm_free_large(exynos_gem->pages);
 }
 
 static int exynos_drm_gem_handle_create(struct drm_gem_object *obj,