[PATCH net 2/2] net/mlx5e: IPsec, fix ASO poll timeout with read_poll_timeout_atomic()

[Tariq Toukan <tariqt@nvidia.com>]

From: Gal Pressman <gal@nvidia.com>

The do-while poll loop uses jiffies for its timeout:
  expires = jiffies + msecs_to_jiffies(10);

jiffies is sampled at an arbitrary point within the current tick, so the
first partial tick contributes anywhere from a full tick down to nearly
zero real time. For small msecs_to_jiffies() results this is
significant, the effective poll window can be much shorter than the
requested 10ms, and in the worst case the loop exits after a single
iteration (e.g., when HZ=100), well before the device has delivered the
CQE.

Replace the loop with read_poll_timeout_atomic(), which counts elapsed
time via udelay() accounting rather than jiffies, guaranteeing the full
poll window regardless of HZ.

Additionally, read_poll_timeout_atomic() executes the poll operation one
more time after the timeout has expired, giving the CQE a final chance
to be detected. The old do-while loop could exit without a final poll if
the timeout expired during the udelay() between iterations.

Fixes: 76e463f6508b ("net/mlx5e: Overcome slow response for first IPsec ASO WQE")
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Jianbo Liu <jianbol@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 .../mellanox/mlx5/core/en_accel/ipsec_offload.c      | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_offload.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_offload.c
index 05faad5083d9..145677ce9640 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_offload.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_offload.c
@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
 /* Copyright (c) 2017, Mellanox Technologies inc. All rights reserved. */
 
+#include <linux/iopoll.h>
+
 #include "mlx5_core.h"
 #include "en.h"
 #include "ipsec.h"
@@ -592,7 +594,6 @@ int mlx5e_ipsec_aso_query(struct mlx5e_ipsec_sa_entry *sa_entry,
 	struct mlx5_wqe_aso_ctrl_seg *ctrl;
 	struct mlx5e_hw_objs *res;
 	struct mlx5_aso_wqe *wqe;
-	unsigned long expires;
 	u8 ds_cnt;
 	int ret;
 
@@ -614,13 +615,8 @@ int mlx5e_ipsec_aso_query(struct mlx5e_ipsec_sa_entry *sa_entry,
 	mlx5e_ipsec_aso_copy(ctrl, data);
 
 	mlx5_aso_post_wqe(aso->aso, false, &wqe->ctrl);
-	expires = jiffies + msecs_to_jiffies(10);
-	do {
-		ret = mlx5_aso_poll_cq(aso->aso, false);
-		if (ret)
-			/* We are in atomic context */
-			udelay(10);
-	} while (ret && time_is_after_jiffies(expires));
+	read_poll_timeout_atomic(mlx5_aso_poll_cq, ret, !ret, 10,
+				 10 * USEC_PER_MSEC, false, aso->aso, false);
 	if (!ret)
 		memcpy(sa_entry->ctx, aso->ctx, MLX5_ST_SZ_BYTES(ipsec_aso));
 	spin_unlock_bh(&aso->lock);
-- 
2.44.0