From: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Subject: S390: Fix mlx5 throughput degradtion
References: jsc#SLE-22496
Patch-mainline: never, interim patch until real cause/fix is found

mlx5 driver checks PCIe bandwidth to decide whether striding should be
enabled. On S390 this check reports a slow pci heuristic, so striding
is disabled. Tests from IBM showed that turning on striding increases
RoCE performance by 25%. As it's not yet clear why S390 PCI is detected
as slow, this interim patch always enables striding for S390.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>

---
 drivers/net/ethernet/mellanox/mlx5/core/en/params.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -304,6 +304,12 @@ void mlx5e_set_rx_cq_mode_params(struct
 				MLX5_CQ_PERIOD_MODE_START_FROM_CQE);
 }
 
+#ifdef CONFIG_S390
+bool slow_pci_heuristic(struct mlx5_core_dev *mdev)
+{
+	return false;
+}
+#else
 bool slow_pci_heuristic(struct mlx5_core_dev *mdev)
 {
 	u32 link_speed = 0;
@@ -319,6 +325,7 @@ bool slow_pci_heuristic(struct mlx5_core
 	return link_speed && pci_bw &&
 		link_speed > MLX5E_SLOW_PCI_RATIO * pci_bw;
 }
+#endif
 
 int mlx5e_mpwrq_validate_regular(struct mlx5_core_dev *mdev, struct mlx5e_params *params)
 {