drm/ttm: Slightly clean up LRU list iteration

To make the transition to using lru hitches easier,
simplify the ttm_resource_manager_next() interface to only take
the cursor and reuse ttm_resource_manager_next() functionality
from ttm_resource_manager_first().

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240705153206.68526-3-thomas.hellstrom@linux.intel.comSigned-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/ttm/ttm_resource.c

@@ -496,48 +496,42 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor)
 {
-	struct ttm_lru_item *lru;
-
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
-				return ttm_lru_item_to_res(lru);
-		}
-
-	return NULL;
+	cursor->priority = 0;
+	cursor->man = man;
+	cursor->cur = &man->lru[cursor->priority];
+	return ttm_resource_manager_next(cursor);
 }
 
 /**
  * ttm_resource_manager_next
  *
- * @man: resource manager to iterate over
  * @cursor: cursor to record the position
- * @res: the current resource pointer
  *
- * Returns the next resource from the resource manager.
+ * Return: the next resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res)
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 {
-	struct ttm_lru_item *lru = &res->lru;
+	struct ttm_resource_manager *man = cursor->man;
+	struct ttm_lru_item *lru;
 
 	lockdep_assert_held(&man->bdev->lru_lock);
 
+	for (;;) {
+		lru = list_entry(cursor->cur, typeof(*lru), link);
 		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
-		if (ttm_lru_item_is_res(lru))
+			if (ttm_lru_item_is_res(lru)) {
+				cursor->cur = &lru->link;
 				return ttm_lru_item_to_res(lru);
 			}
+		}
 
-	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
-				ttm_lru_item_to_res(lru);
+		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
+			break;
+
+		cursor->cur = &man->lru[cursor->priority];
 	}
 
 	return NULL;

include/drm/ttm/ttm_resource.h

@@ -272,11 +272,15 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
 /**
  * struct ttm_resource_cursor
  *
+ * @man: The resource manager currently being iterated over.
+ * @cur: The list head the cursor currently points to.
  * @priority: the current priority
  *
  * Cursor to iterate over the resources in a manager.
  */
 struct ttm_resource_cursor {
+	struct ttm_resource_manager *man;
+	struct list_head *cur;
 	unsigned int priority;
 };
 
@@ -438,9 +442,7 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor);
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res);
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
 
 struct ttm_resource *
 ttm_lru_first_res_or_null(struct list_head *head);
@@ -455,7 +457,7 @@ ttm_lru_first_res_or_null(struct list_head *head);
  */
 #define ttm_resource_manager_for_each_res(man, cursor, res)		\
 	for (res = ttm_resource_manager_first(man, cursor); res;	\
-	     res = ttm_resource_manager_next(man, cursor, res))
+	     res = ttm_resource_manager_next(cursor))
 
 struct ttm_kmap_iter *
 ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,