net/mlx5: Introduce hierarchy level tracking on scheduling nodes

Add a `level` field to `mlx5_esw_sched_node` to track the hierarchy
depth of each scheduling node. This allows enforcement of the
scheduling depth constraints based on `log_esw_max_sched_depth`.

Modify `esw_qos_node_set_parent()` and `__esw_qos_alloc_node()` to
correctly assign hierarchy levels. Ensure that nodes inherit their
parent’s level incrementally.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1741642016-44918-3-git-send-email-tariqt@nvidia.com
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: cjubran

drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c

@@ -90,15 +90,30 @@ struct mlx5_esw_sched_node {
 	struct list_head children;
 	/* Valid only if this node is associated with a vport. */
 	struct mlx5_vport *vport;
+	/* Level in the hierarchy. The root node level is 1. */
+	u8 level;
 };
 
+static void esw_qos_node_attach_to_parent(struct mlx5_esw_sched_node *node)
+{
+	if (!node->parent) {
+		/* Root children are assigned a depth level of 2. */
+		node->level = 2;
+		list_add_tail(&node->entry, &node->esw->qos.domain->nodes);
+	} else {
+		node->level = node->parent->level + 1;
+		list_add_tail(&node->entry, &node->parent->children);
+	}
+}
+
 static void
 esw_qos_node_set_parent(struct mlx5_esw_sched_node *node, struct mlx5_esw_sched_node *parent)
 {
 	list_del_init(&node->entry);
 	node->parent = parent;
 	list_add_tail(&node->entry, &parent->children);
 	node->esw = parent->esw;
+	node->level = parent->level + 1;
 }
 
 void mlx5_esw_qos_vport_qos_free(struct mlx5_vport *vport)
@@ -358,7 +373,6 @@ static struct mlx5_esw_sched_node *
 __esw_qos_alloc_node(struct mlx5_eswitch *esw, u32 tsar_ix, enum sched_node_type type,
 		     struct mlx5_esw_sched_node *parent)
 {
-	struct list_head *parent_children;
 	struct mlx5_esw_sched_node *node;
 
 	node = kzalloc(sizeof(*node), GFP_KERNEL);
@@ -370,8 +384,7 @@ __esw_qos_alloc_node(struct mlx5_eswitch *esw, u32 tsar_ix, enum sched_node_type
 	node->type = type;
 	node->parent = parent;
 	INIT_LIST_HEAD(&node->children);
-	parent_children = parent ? &parent->children : &esw->qos.domain->nodes;
-	list_add_tail(&node->entry, parent_children);
+	esw_qos_node_attach_to_parent(node);
 
 	return node;
 }