net/mlx5: Fix FW tracer timestamp calculation

[ Upstream commit 61db3d7b99 ]

Fix a bug in calculation of FW tracer timestamp. Decreasing one in the
calculation should effect only bits 52_7 and not effect bits 6_0 of the
timestamp, otherwise bits 6_0 are always set in this calculation.

Fixes: 70dd6fdb89 ("net/mlx5: FW tracer, parse traces and kernel tracing support")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Feras Daoud <ferasda@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c

@@ -638,7 +638,7 @@ static void mlx5_tracer_handle_timestamp_trace(struct mlx5_fw_tracer *tracer,
 			trace_timestamp = (timestamp_event.timestamp & MASK_52_7) |
 					  (str_frmt->timestamp & MASK_6_0);
 		else
-			trace_timestamp = ((timestamp_event.timestamp & MASK_52_7) - 1) |
+			trace_timestamp = ((timestamp_event.timestamp - 1) & MASK_52_7) |
 					  (str_frmt->timestamp & MASK_6_0);
 
 		mlx5_tracer_print_trace(str_frmt, dev, trace_timestamp);