drm/exynos: fix DMA_ATTR_NO_KERNEL_MAPPING usage

The Exynos DRM driver doesn't follow the correct API when dealing with
dma_{alloc, mmap, free}_attrs functions and the
DMA_ATTR_NO_KERNEL_MAPPING attribute.

When a IOMMU is not available and the DMA_ATTR_NO_KERNEL_MAPPING is
used, the driver should use the pointer returned by dma_alloc_attr() as
a cookie.

The Exynos DRM driver directly uses the non-requested virtual kernel
address returned by the DMA mapping subsystem. This just works now
because the non-IOMMU codepath doesn't obey DMA_ATTR_NO_KERNEL_MAPPING
but we need to fix it before fixing the DMA layer.

Signed-off-by: Carlo Caione <carlo@caione.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_buf.c

@@ -63,11 +63,11 @@ static int lowlevel_buffer_allocate(struct drm_device *dev,
 			return -ENOMEM;
 		}
 
-		buf->kvaddr = (void __iomem *)dma_alloc_attrs(dev->dev,
+		buf->cookie = dma_alloc_attrs(dev->dev,
 					buf->size,
 					&buf->dma_addr, GFP_KERNEL,
 					&buf->dma_attrs);
-		if (!buf->kvaddr) {
+		if (!buf->cookie) {
 			DRM_ERROR("failed to allocate buffer.\n");
 			ret = -ENOMEM;
 			goto err_free;
@@ -132,7 +132,7 @@ static void lowlevel_buffer_deallocate(struct drm_device *dev,
 	buf->sgt = NULL;
 
 	if (!is_drm_iommu_supported(dev)) {
-		dma_free_attrs(dev->dev, buf->size, buf->kvaddr,
+		dma_free_attrs(dev->dev, buf->size, buf->cookie,
 				(dma_addr_t)buf->dma_addr, &buf->dma_attrs);
 		drm_free_large(buf->pages);
 	} else

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

@@ -79,9 +79,9 @@ static int exynos_drm_fbdev_update(struct drm_fb_helper *helper,
 				     struct drm_framebuffer *fb)
 {
 	struct fb_info *fbi = helper->fbdev;
-	struct drm_device *dev = helper->dev;
 	struct exynos_drm_gem_buf *buffer;
 	unsigned int size = fb->width * fb->height * (fb->bits_per_pixel >> 3);
+	unsigned int nr_pages;
 	unsigned long offset;
 
 	drm_fb_helper_fill_fix(fbi, fb->pitches[0], fb->depth);
@@ -94,25 +94,14 @@ static int exynos_drm_fbdev_update(struct drm_fb_helper *helper,
 		return -EFAULT;
 	}
 
-	/* map pages with kernel virtual space. */
+	nr_pages = buffer->size >> PAGE_SHIFT;
+
+	buffer->kvaddr = (void __iomem *) vmap(buffer->pages,
+			nr_pages, VM_MAP,
+			pgprot_writecombine(PAGE_KERNEL));
 	if (!buffer->kvaddr) {
-		if (is_drm_iommu_supported(dev)) {
-			unsigned int nr_pages = buffer->size >> PAGE_SHIFT;
-
-			buffer->kvaddr = (void __iomem *) vmap(buffer->pages,
-					nr_pages, VM_MAP,
-					pgprot_writecombine(PAGE_KERNEL));
-		} else {
-			phys_addr_t dma_addr = buffer->dma_addr;
-			if (dma_addr)
-				buffer->kvaddr = (void __iomem *)phys_to_virt(dma_addr);
-			else
-				buffer->kvaddr = (void __iomem *)NULL;
-		}
-		if (!buffer->kvaddr) {
-			DRM_ERROR("failed to map pages to kernel space.\n");
-			return -EIO;
-		}
+		DRM_ERROR("failed to map pages to kernel space.\n");
+		return -EIO;
 	}
 
 	/* buffer count to framebuffer always is 1 at booting time. */
@@ -313,7 +302,7 @@ static void exynos_drm_fbdev_destroy(struct drm_device *dev,
 	struct exynos_drm_gem_obj *exynos_gem_obj = exynos_fbd->exynos_gem_obj;
 	struct drm_framebuffer *fb;
 
-	if (is_drm_iommu_supported(dev) && exynos_gem_obj->buffer->kvaddr)
+	if (exynos_gem_obj->buffer->kvaddr)
 		vunmap(exynos_gem_obj->buffer->kvaddr);
 
 	/* release drm framebuffer and real buffer */

drivers/gpu/drm/exynos/exynos_drm_gem.h

@@ -22,6 +22,7 @@
 /*
  * exynos drm gem buffer structure.
  *
+ * @cookie: cookie returned by dma_alloc_attrs
  * @kvaddr: kernel virtual address to allocated memory region.
  * *userptr: user space address.
  * @dma_addr: bus address(accessed by dma) to allocated memory region.
@@ -35,6 +36,7 @@
  *	VM_PFNMAP or not.
  */
 struct exynos_drm_gem_buf {
+	void 			*cookie;
 	void __iomem		*kvaddr;
 	unsigned long		userptr;
 	dma_addr_t		dma_addr;