net/mlx5e: Add support for PCI relaxed ordering

The concept of Relaxed Ordering in the PCI Express environment allows
switches in the path between the Requester and Completer to reorder some
transactions just received before others that were previously enqueued.

In ETH driver, there is no question of write integrity since each memory
segment is written only once per cycle. In addition, the driver doesn't
access the memory shared with the hardware until the corresponding CQE
arrives indicating all PCI transactions are done.

Running TCP single stream over ConnectX-4 LX, ARM CPU on remote-numa has
300% improvement in the bandwidth.

With relaxed ordering turned off: BW:10 [GB/s]
With relaxed ordering turned on: BW:40 [GB/s]

The driver turns relaxed ordering with respect to the firmware
capabilities and the return value from pcie_relaxed_ordering_enabled().
Signed-off-by: Aya Levin <ayal@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en.h

@@ -974,6 +974,7 @@ int mlx5e_create_mdev_resources(struct mlx5_core_dev *mdev);
 void mlx5e_destroy_mdev_resources(struct mlx5_core_dev *mdev);
 int mlx5e_refresh_tirs(struct mlx5e_priv *priv, bool enable_uc_lb,
 		       bool enable_mc_lb);
+void mlx5e_mkey_set_relaxed_ordering(struct mlx5_core_dev *mdev, void *mkc);
 
 /* common netdev helpers */
 void mlx5e_create_q_counters(struct mlx5e_priv *priv);

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

@@ -60,6 +60,16 @@ void mlx5e_destroy_tir(struct mlx5_core_dev *mdev,
 	mutex_unlock(&mdev->mlx5e_res.td.list_lock);
 }
 
+void mlx5e_mkey_set_relaxed_ordering(struct mlx5_core_dev *mdev, void *mkc)
+{
+	bool ro_pci_enable = pcie_relaxed_ordering_enabled(mdev->pdev);
+	bool ro_write = MLX5_CAP_GEN(mdev, relaxed_ordering_write);
+	bool ro_read = MLX5_CAP_GEN(mdev, relaxed_ordering_read);
+
+	MLX5_SET(mkc, mkc, relaxed_ordering_read, ro_pci_enable && ro_read);
+	MLX5_SET(mkc, mkc, relaxed_ordering_write, ro_pci_enable && ro_write);
+}
+
 static int mlx5e_create_mkey(struct mlx5_core_dev *mdev, u32 pdn,
 			     struct mlx5_core_mkey *mkey)
 {
@@ -76,7 +86,7 @@ static int mlx5e_create_mkey(struct mlx5_core_dev *mdev, u32 pdn,
 	MLX5_SET(mkc, mkc, access_mode_1_0, MLX5_MKC_ACCESS_MODE_PA);
 	MLX5_SET(mkc, mkc, lw, 1);
 	MLX5_SET(mkc, mkc, lr, 1);
-
+	mlx5e_mkey_set_relaxed_ordering(mdev, mkc);
 	MLX5_SET(mkc, mkc, pd, pdn);
 	MLX5_SET(mkc, mkc, length64, 1);
 	MLX5_SET(mkc, mkc, qpn, 0xffffff);

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

@@ -274,7 +274,7 @@ static int mlx5e_create_umr_mkey(struct mlx5_core_dev *mdev,
 	MLX5_SET(mkc, mkc, lw, 1);
 	MLX5_SET(mkc, mkc, lr, 1);
 	MLX5_SET(mkc, mkc, access_mode_1_0, MLX5_MKC_ACCESS_MODE_MTT);
-
+	mlx5e_mkey_set_relaxed_ordering(mdev, mkc);
 	MLX5_SET(mkc, mkc, qpn, 0xffffff);
 	MLX5_SET(mkc, mkc, pd, mdev->mlx5e_res.pdn);
 	MLX5_SET64(mkc, mkc, len, npages << page_shift);