ethtool: linkstate: add a statistic for PHY down events

The previous attempt to augment carrier_down (see Link)
was not met with much enthusiasm so let's do the simple
thing of exposing what some devices already maintain.
Add a common ethtool statistic for link going down.
Currently users have to maintain per-driver mapping
to extract the right stat from the vendor-specific ethtool -S
stats. carrier_down does not fit the bill because it counts
a lot of software related false positives.

Add the statistic to the extended link state API to steer
vendors towards implementing all of it.

Implement for bnxt and all Linux-controlled PHYs. mlx5 and (possibly)
enic also have a counter for this but I leave the implementation
to their maintainers.

Link: https://lore.kernel.org/r/20220520004500.2250674-1-kuba@kernel.org
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20221104190125.684910-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/net/ethtool/linkstate.c b/net/ethtool/linkstate.c
index fb676f349455..2158c17a0b32 100644
--- a/net/ethtool/linkstate.c
+++ b/net/ethtool/linkstate.c
@@ -13,6 +13,7 @@ struct linkstate_reply_data {
 	int					link;
 	int					sqi;
 	int					sqi_max;
+	struct ethtool_link_ext_stats		link_stats;
 	bool					link_ext_state_provided;
 	struct ethtool_link_ext_state_info	ethtool_link_ext_state_info;
 };
@@ -22,7 +23,7 @@ struct linkstate_reply_data {
 
 const struct nla_policy ethnl_linkstate_get_policy[] = {
 	[ETHTOOL_A_LINKSTATE_HEADER]		=
-		NLA_POLICY_NESTED(ethnl_header_policy),
+		NLA_POLICY_NESTED(ethnl_header_policy_stats),
 };
 
 static int linkstate_get_sqi(struct net_device *dev)
@@ -107,6 +108,19 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
 			goto out;
 	}
 
+	ethtool_stats_init((u64 *)&data->link_stats,
+			   sizeof(data->link_stats) / 8);
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS) {
+		if (dev->phydev)
+			data->link_stats.link_down_events =
+				READ_ONCE(dev->phydev->link_down_events);
+
+		if (dev->ethtool_ops->get_link_ext_stats)
+			dev->ethtool_ops->get_link_ext_stats(dev,
+							     &data->link_stats);
+	}
+
 	ret = 0;
 out:
 	ethnl_ops_complete(dev);
@@ -134,6 +148,9 @@ static int linkstate_reply_size(const struct ethnl_req_info *req_base,
 	if (data->ethtool_link_ext_state_info.__link_ext_substate)
 		len += nla_total_size(sizeof(u8)); /* LINKSTATE_EXT_SUBSTATE */
 
+	if (data->link_stats.link_down_events != ETHTOOL_STAT_NOT_SET)
+		len += nla_total_size(sizeof(u32));
+
 	return len;
 }
 
@@ -166,6 +183,11 @@ static int linkstate_fill_reply(struct sk_buff *skb,
 			return -EMSGSIZE;
 	}
 
+	if (data->link_stats.link_down_events != ETHTOOL_STAT_NOT_SET)
+		if (nla_put_u32(skb, ETHTOOL_A_LINKSTATE_EXT_DOWN_CNT,
+				data->link_stats.link_down_events))
+			return -EMSGSIZE;
+
 	return 0;
 }