drm/exynos: Use FOLL_LONGTERM for g2d cmdlists

The exynos g2d interface is very unusual, but it looks like the
userptr objects are persistent. Hence they need FOLL_LONGTERM.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-3-daniel.vetter@ffwll.ch

drivers/gpu/drm/exynos/exynos_drm_g2d.c

@@ -475,7 +475,8 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d,
 		goto err_free;
 	}
 
-	ret = pin_user_pages_fast(start, npages, FOLL_FORCE | FOLL_WRITE,
+	ret = pin_user_pages_fast(start, npages,
+				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
 				  g2d_userptr->pages);
 	if (ret != npages) {
 		DRM_DEV_ERROR(g2d->dev,