drm/rockchip: avoid duplicate mappings for IOMMU devices

If a buffer is allocated with alloc_kmap, then it is vmap'd on creation
and there is no reason to map it again in rockchip_gem_prime_vmap() when
the existing mapping can be used.
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20221110172415.2853420-1-john@metanate.com

drivers/gpu/drm/rockchip/rockchip_drm_gem.c

@@ -519,8 +519,14 @@ int rockchip_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
 
 	if (rk_obj->pages) {
-		void *vaddr = vmap(rk_obj->pages, rk_obj->num_pages, VM_MAP,
-				  pgprot_writecombine(PAGE_KERNEL));
+		void *vaddr;
+
+		if (rk_obj->kvaddr)
+			vaddr = rk_obj->kvaddr;
+		else
+			vaddr = vmap(rk_obj->pages, rk_obj->num_pages, VM_MAP,
+				     pgprot_writecombine(PAGE_KERNEL));
+
 		if (!vaddr)
 			return -ENOMEM;
 		iosys_map_set_vaddr(map, vaddr);
@@ -540,7 +546,8 @@ void rockchip_gem_prime_vunmap(struct drm_gem_object *obj,
 	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
 
 	if (rk_obj->pages) {
-		vunmap(map->vaddr);
+		if (map->vaddr != rk_obj->kvaddr)
+			vunmap(map->vaddr);
 		return;
 	}