drm/exynos: Fix dma-buf import

When IOMMU support was enabled, dma-buf import in Exynos DRM was broken
since commit f43c35966a5a ("drm/exynos: use real device for DMA-mapping
operations") due to using wrong struct device in drm_gem_prime_import()
function. This patch fixes following kernel BUG caused by incorrect buffer
mapping to DMA address space:

exynos-sysmmu 14650000.sysmmu: 14450000.mixer: PAGE FAULT occurred at 0xb2e00000
------------[ cut here ]------------
kernel BUG at drivers/iommu/exynos-iommu.c:449!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc4-next-20171016-00033-g990d723669fd #3165
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
task: c0e0b7c0 task.stack: c0e00000
PC is at exynos_sysmmu_irq+0x1d0/0x24c
LR is at exynos_sysmmu_irq+0x154/0x24c
------------[ cut here ]------------

Reported-by: Marian Mihailescu <mihailescu2m@gmail.com>
Fixes: f43c35966a5a ("drm/exynos: use real device for DMA-mapping operations")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -148,7 +148,7 @@ static struct drm_driver exynos_drm_driver = {
 	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
 	.gem_prime_export	= drm_gem_prime_export,
-	.gem_prime_import	= drm_gem_prime_import,
+	.gem_prime_import	= exynos_drm_gem_prime_import,
 	.gem_prime_get_sg_table	= exynos_drm_gem_prime_get_sg_table,
 	.gem_prime_import_sg_table	= exynos_drm_gem_prime_import_sg_table,
 	.gem_prime_vmap		= exynos_drm_gem_prime_vmap,

drivers/gpu/drm/exynos/exynos_drm_gem.c

@@ -506,6 +506,12 @@ int exynos_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 }
 
 /* low-level interface prime helpers */
+struct drm_gem_object *exynos_drm_gem_prime_import(struct drm_device *dev,
+					    struct dma_buf *dma_buf)
+{
+	return drm_gem_prime_import_dev(dev, dma_buf, to_dma_dev(dev));
+}
+
 struct sg_table *exynos_drm_gem_prime_get_sg_table(struct drm_gem_object *obj)
 {
 	struct exynos_drm_gem *exynos_gem = to_exynos_gem(obj);

drivers/gpu/drm/exynos/exynos_drm_gem.h

@@ -117,6 +117,8 @@ int exynos_drm_gem_fault(struct vm_fault *vmf);
 int exynos_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
 
 /* low-level interface prime helpers */
+struct drm_gem_object *exynos_drm_gem_prime_import(struct drm_device *dev,
+					    struct dma_buf *dma_buf);
 struct sg_table *exynos_drm_gem_prime_get_sg_table(struct drm_gem_object *obj);
 struct drm_gem_object *
 exynos_drm_gem_prime_import_sg_table(struct drm_device *dev,