net/mlx5e: RX, Fix wrong early return in receive queue poll

When the completion queue of the RQ is empty, do not immediately return.
If left-over decompressed CQEs (from the previous cycle) were processed,
need to go to the finalization part of the poll function.

Bug exists only when CQE compression is turned ON.

This solves the following issue:
mlx5_core 0000:82:00.1: mlx5_eq_int:544:(pid 0): CQ error on CQN 0xc08, syndrome 0x1
mlx5_core 0000:82:00.1 p4p2: mlx5e_cq_error_event: cqn=0x000c08 event=0x04

Fixes: 4b7dfc99 ("net/mlx5e: Early-return on empty completion queues")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

@@ -1190,7 +1190,7 @@ void mlx5e_handle_rx_cqe_mpwrq(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe)
 int mlx5e_poll_rx_cq(struct mlx5e_cq *cq, int budget)
 {
 	struct mlx5e_rq *rq = container_of(cq, struct mlx5e_rq, cq);
-	struct mlx5e_xdpsq *xdpsq;
+	struct mlx5e_xdpsq *xdpsq = &rq->xdpsq;
 	struct mlx5_cqe64 *cqe;
 	int work_done = 0;
 
@@ -1201,10 +1201,11 @@ int mlx5e_poll_rx_cq(struct mlx5e_cq *cq, int budget)
 		work_done += mlx5e_decompress_cqes_cont(rq, cq, 0, budget);
 
 	cqe = mlx5_cqwq_get_cqe(&cq->wq);
-	if (!cqe)
+	if (!cqe) {
+		if (unlikely(work_done))
+			goto out;
 		return 0;
-
-	xdpsq = &rq->xdpsq;
+	}
 
 	do {
 		if (mlx5_get_cqe_format(cqe) == MLX5_COMPRESSED) {
@@ -1219,6 +1220,7 @@ int mlx5e_poll_rx_cq(struct mlx5e_cq *cq, int budget)
 		rq->handle_rx_cqe(rq, cqe);
 	} while ((++work_done < budget) && (cqe = mlx5_cqwq_get_cqe(&cq->wq)));
 
+out:
 	if (xdpsq->doorbell) {
 		mlx5e_xmit_xdp_doorbell(xdpsq);
 		xdpsq->doorbell = false;