netdev - [net-next 16/17] net/mlx5e: RX, Always prefer Linear SKB configuration

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Date:   Fri,  1 Jun 2018 17:05:43 -0700
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [net-next 16/17] net/mlx5e: RX, Always prefer Linear SKB configuration

From: Tariq Toukan <tariqt@...lanox.com>

Prefer the linear SKB configuration of Legacy RQ over the
non-linear one of Striding RQ.

This implies that ConnectX-4 LX now uses legacy RQ by default,
as it does not support the linear configuration of Striding RQ.

Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 2c634e50d051..333d4ed52b94 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -4405,9 +4405,16 @@ void mlx5e_build_nic_params(struct mlx5_core_dev *mdev,
 	MLX5E_SET_PFLAG(params, MLX5E_PFLAG_RX_CQE_COMPRESS, params->rx_cqe_compress_def);
 
 	/* RQ */
-	if (mlx5e_striding_rq_possible(mdev, params))
-		MLX5E_SET_PFLAG(params, MLX5E_PFLAG_RX_STRIDING_RQ,
-				!slow_pci_heuristic(mdev));
+	/* Prefer Striding RQ, unless any of the following holds:
+	 * - Striding RQ configuration is not possible/supported.
+	 * - Slow PCI heuristic.
+	 * - Legacy RQ would use linear SKB while Striding RQ would use non-linear.
+	 */
+	if (!slow_pci_heuristic(mdev) &&
+	    mlx5e_striding_rq_possible(mdev, params) &&
+	    (mlx5e_rx_mpwqe_is_linear_skb(mdev, params) ||
+	     !mlx5e_rx_is_linear_skb(mdev, params)))
+		MLX5E_SET_PFLAG(params, MLX5E_PFLAG_RX_STRIDING_RQ, true);
 	mlx5e_set_rq_type(mdev, params);
 	mlx5e_init_rq_type_params(mdev, params);
 
-- 
2.17.0