net/mlx5e: Fix number of lanes to UNKNOWN when using data_rate_oper

JIRA: https://issues.redhat.com/browse/RHEL-72227
JIRA: https://issues.redhat.com/browse/RHEL-73520
Upstream-status: v6.16-rc2

commit 875d7c1
Author: Shahar Shitrit <shshitrit@nvidia.com>
Date:   Tue Jun 10 18:15:14 2025 +0300

    net/mlx5e: Fix number of lanes to UNKNOWN when using data_rate_oper

    When the link is up, either eth_proto_oper or ext_eth_proto_oper
    typically reports the active link protocol, from which both speed
    and number of lanes can be retrieved. However, in certain cases,
    such as when a NIC is connected via a non-standard cable, the
    firmware may not report the protocol.

    In such scenarios, the speed can still be obtained from the
    data_rate_oper field in PTYS register. Since data_rate_oper
    provides only speed information and lacks lane details, it is
    incorrect to derive the number of lanes from it.

    This patch corrects the behavior by setting the number of lanes to
    UNKNOWN instead of incorrectly using MAX_LANES when relying on
    data_rate_oper.

    Fixes: 7e95979 ("net/mlx5e: Enable lanes configuration when auto-negotiation is off")
    Signed-off-by: Shahar Shitrit <shshitrit@nvidia.com>
    Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
    Signed-off-by: Mark Bloch <mbloch@nvidia.com>
    Link: https://patch.msgid.link/20250610151514.1094735-10-mbloch@nvidia.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Benjamin Poirier <bpoirier@redhat.com>

Author: Benjamin Poirier

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

@@ -43,7 +43,6 @@
 #include "en/fs_ethtool.h"
 
 #define LANES_UNKNOWN		 0
-#define MAX_LANES		 8
 
 void mlx5e_ethtool_get_drvinfo(struct mlx5e_priv *priv,
 			       struct ethtool_drvinfo *drvinfo)
@@ -1098,10 +1097,8 @@ static void get_link_properties(struct net_device *netdev,
 		speed = info->speed;
 		lanes = info->lanes;
 		duplex = DUPLEX_FULL;
-	} else if (data_rate_oper) {
+	} else if (data_rate_oper)
 		speed = 100 * data_rate_oper;
-		lanes = MAX_LANES;
-	}
 
 out:
 	link_ksettings->base.duplex = duplex;