Re: [PATCH iwl-net v3 2/3] ice: fix autoneg disable when link partner doesn't support AN

From: Konrad Knitter <redacted>

Disabling autonegotiation was silently ignored when autoneg had not yet
completed (ICE_AQ_AN_COMPLETED was not set), leaving the configuration
unchanged with no error. This could prevent link from forming if the
link partner requires non-autoneg mode.

Extend the condition to also allow disabling autoneg when the link
partner reports no AN ability (ICE_AQ_LP_AN_ABILITY clear). Gate the
ICE_AQ_LP_AN_ABILITY check on the link being up so that stale or
zeroed an_info when link is down does not produce a false positive.
Introduce the helper ice_autoneg_disable_allowed() to make the check
explicit.

Fixes: f1a4a66d2310 ("ice: fix set pause param autoneg check")
Signed-off-by: Konrad Knitter <redacted>
Signed-off-by: Aleksandr Loktionov <redacted>
Reviewed-by: Simon Horman <horms@kernel.org>
---
 drivers/net/ethernet/intel/ice/ice_ethtool.c | 26 ++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
index a257b7d..4ce198f 100644
--- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
+++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c

@@ -2501,6 +2501,28 @@ ice_ksettings_find_adv_link_speed(const struct ethtool_link_ksettings *ks)
 	return adv_link_speed;
 }
 
+/**
+ * ice_autoneg_disable_allowed - check if autoneg can be disabled
+ * @p: port info
+ *
+ * Check if autonegotiation can be disabled based on link state.
+ * ICE_AQ_LP_AN_ABILITY is only valid when the link is up; gate that
+ * check accordingly to avoid false positives from stale link data.
+ *
+ * Return: true if autoneg has completed, or if the link is up and the
+ *         link partner does not advertise autonegotiation capability.
+ */
+static bool ice_autoneg_disable_allowed(struct ice_port_info *p)
+{
+	u8 an_info = p->phy.link_info.an_info;
+
+	if (an_info & ICE_AQ_AN_COMPLETED)
+		return true;
+	/* ICE_AQ_LP_AN_ABILITY is only valid when link is up */
+	return (p->phy.link_info.link_info & ICE_AQ_LINK_UP) &&
+	       !(an_info & ICE_AQ_LP_AN_ABILITY);
+}
+
 /**
  * ice_setup_autoneg
  * @p: port info

@@ -2539,8 +2561,8 @@ ice_setup_autoneg(struct ice_port_info *p, struct ethtool_link_ksettings *ks,
 			}
 		}
 	} else {
-		/* If autoneg is currently enabled */
-		if (p->phy.link_info.an_info & ICE_AQ_AN_COMPLETED) {
+		/* If autoneg completed or link partner does not support AN */
+		if (ice_autoneg_disable_allowed(p)) {
 			/* If autoneg is supported 10GBASE_T is the only PHY
 			 * that can disable it, so otherwise return error
 			 */