Based on https://github.com/geerlingguy/raspberry-pi-pcie-devices/discussions/756

Modified to upstream w/ CONFIG_X86

---
 drivers/gpu/drm/ttm/ttm_bo_util.c | 14 +-------------
 drivers/gpu/drm/ttm/ttm_module.c  |  5 +++++
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 0b3f4267130c..e0e55cb9edd2 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -343,8 +343,10 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 		.no_wait_gpu = false
 	};
 	struct ttm_tt *ttm = bo->ttm;
+#if !defined(CONFIG_ARM64)
 	struct ttm_resource_manager *man =
 			ttm_manager_type(bo->bdev, bo->resource->mem_type);
+#endif
 	pgprot_t prot;
 	int ret;
 
@@ -354,17 +352,20 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 	if (ret)
 		return ret;

+#if !defined(CONFIG_ARM64)
 	if (num_pages == 1 && ttm->caching == ttm_cached &&
 	    !(man->use_tt && (ttm->page_flags & TTM_TT_FLAG_DECRYPTED))) {
 		/*
 		 * We're mapping a single page, and the desired
 		 * page protection is consistent with the bo.
 		 */
 
 		map->bo_kmap_type = ttm_bo_map_kmap;
 		map->page = ttm->pages[start_page];
 		map->virtual = kmap(map->page);
-	} else {
+	} else
+#endif
+	{
 		/*
 		 * We need to use vmap to get the desired page protection
 		 * or to make the buffer object look contiguous.
diff --git a/drivers/gpu/drm/ttm/ttm_module.c b/drivers/gpu/drm/ttm/ttm_module.c
index b3fffe7b5062..9f3e425626b5 100644
--- a/drivers/gpu/drm/ttm/ttm_module.c
+++ b/drivers/gpu/drm/ttm/ttm_module.c
@@ -63,7 +63,13 @@ pgprot_t ttm_prot_from_caching(enum ttm_caching caching, pgprot_t tmp)
 {
 	/* Cached mappings need no adjustment */
 	if (caching == ttm_cached)
+	{
+#if !defined(CONFIG_ARM64)
 		return tmp;
+#else
+		return pgprot_dmacoherent(tmp);
+#endif
+	}
 
 #if defined(__i386__) || defined(__x86_64__)
 	if (caching == ttm_write_combined)
-- 
2.49.0