drm/ttm: partial revert "cleanup ttm_tt_(unbind|destroy)" v3

We still need to unbind explicitly during a move.

This partial reverts commit ff20caa0bcbfef9f7686f8d1868a3b990921afd6.

v2: remove unnecessary check and unused variable
v3: fix typo in commit message

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -53,6 +53,7 @@ int ttm_bo_move_ttm(struct ttm_buffer_object *bo,
 	int ret;
 
 	if (old_mem->mem_type != TTM_PL_SYSTEM) {
+		ttm_tt_unbind(ttm);
 		ttm_bo_free_old_node(bo);
 		ttm_flag_masked(&old_mem->placement, TTM_PL_FLAG_SYSTEM,
 				TTM_PL_MASK_MEM);

drivers/gpu/drm/ttm/ttm_tt.c

@@ -166,16 +166,10 @@ EXPORT_SYMBOL(ttm_tt_set_placement_caching);
 
 void ttm_tt_destroy(struct ttm_tt *ttm)
 {
-	int ret;
-
 	if (ttm == NULL)
 		return;
 
-	if (ttm->state == tt_bound) {
-		ret = ttm->func->unbind(ttm);
-		BUG_ON(ret);
-		ttm->state = tt_unbound;
-	}
+	ttm_tt_unbind(ttm);
 
 	if (ttm->state == tt_unbound)
 		ttm_tt_unpopulate(ttm);
@@ -255,6 +249,17 @@ void ttm_dma_tt_fini(struct ttm_dma_tt *ttm_dma)
 }
 EXPORT_SYMBOL(ttm_dma_tt_fini);
 
+void ttm_tt_unbind(struct ttm_tt *ttm)
+{
+	int ret;
+
+	if (ttm->state == tt_bound) {
+		ret = ttm->func->unbind(ttm);
+		BUG_ON(ret);
+		ttm->state = tt_unbound;
+	}
+}
+
 int ttm_tt_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem)
 {
 	int ret = 0;

include/drm/ttm/ttm_bo_driver.h

@@ -627,6 +627,15 @@ extern int ttm_tt_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem);
  */
 extern void ttm_tt_destroy(struct ttm_tt *ttm);
 
+/**
+ * ttm_ttm_unbind:
+ *
+ * @ttm: The struct ttm_tt.
+ *
+ * Unbind a struct ttm_tt.
+ */
+extern void ttm_tt_unbind(struct ttm_tt *ttm);
+
 /**
  * ttm_tt_swapin:
  *