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>

diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index d578b8b..bede24e 100644 (file)
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -491,6 +491,7 @@ Kernel response contents:
   ``ETHTOOL_A_LINKSTATE_SQI_MAX``       u32     Max support SQI value
   ``ETHTOOL_A_LINKSTATE_EXT_STATE``     u8      link extended state
   ``ETHTOOL_A_LINKSTATE_EXT_SUBSTATE``  u8      link extended substate
+  ``ETHTOOL_A_LINKSTATE_EXT_DOWN_CNT``  u32     count of link down events
   ====================================  ======  ============================
 
 For most NIC drivers, the value of ``ETHTOOL_A_LINKSTATE_LINK`` returns

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index cc89e5e..d8f0351 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -4112,6 +4112,20 @@ static void bnxt_get_rmon_stats(struct net_device *dev,
        *ranges = bnxt_rmon_ranges;
 }
 
+static void bnxt_get_link_ext_stats(struct net_device *dev,
+                                   struct ethtool_link_ext_stats *stats)
+{
+       struct bnxt *bp = netdev_priv(dev);
+       u64 *rx;
+
+       if (BNXT_VF(bp) || !(bp->flags & BNXT_FLAG_PORT_STATS_EXT))
+               return;
+
+       rx = bp->rx_port_stats_ext.sw_stats;
+       stats->link_down_events =
+               *(rx + BNXT_RX_STATS_EXT_OFFSET(link_down_events));
+}
+
 void bnxt_ethtool_free(struct bnxt *bp)
 {
        kfree(bp->test_info);
@@ -4161,6 +4175,7 @@ const struct ethtool_ops bnxt_ethtool_ops = {
        .get_eeprom             = bnxt_get_eeprom,
        .set_eeprom             = bnxt_set_eeprom,
        .get_link               = bnxt_get_link,
+       .get_link_ext_stats     = bnxt_get_link_ext_stats,
        .get_eee                = bnxt_get_eee,
        .set_eee                = bnxt_set_eee,
        .get_module_info        = bnxt_get_module_info,

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index e741d8a..e5b6cb1 100644 (file)
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -67,6 +67,7 @@ static void phy_link_down(struct phy_device *phydev)
 {
        phydev->phy_link_change(phydev, false);
        phy_led_trigger_change_speed(phydev);
+       WRITE_ONCE(phydev->link_down_events, phydev->link_down_events + 1);
 }
 
 static const char *phy_pause_str(struct phy_device *phydev)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 99dc7bf..5c51c7f 100644 (file)
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -125,6 +125,20 @@ struct ethtool_link_ext_state_info {
        };
 };
 
+struct ethtool_link_ext_stats {
+       /* Custom Linux statistic for PHY level link down events.
+        * In a simpler world it should be equal to netdev->carrier_down_count
+        * unfortunately netdev also counts local reconfigurations which don't
+        * actually take the physical link down, not to mention NC-SI which,
+        * if present, keeps the link up regardless of host state.
+        * This statistic counts when PHY _actually_ went down, or lost link.
+        *
+        * Note that we need u64 for ethtool_stats_init() and comparisons
+        * to ETHTOOL_STAT_NOT_SET, but only u32 is exposed to the user.
+        */
+       u64 link_down_events;
+};
+
 /**
  * ethtool_rxfh_indir_default - get default value for RX flow hash indirection
  * @index: Index in RX flow hash indirection table
@@ -481,6 +495,7 @@ struct ethtool_module_power_mode_params {
  *     do not attach ext_substate attribute to netlink message). If link_ext_state
  *     and link_ext_substate are unknown, return -ENODATA. If not implemented,
  *     link_ext_state and link_ext_substate will not be sent to userspace.
+ * @get_link_ext_stats: Read extra link-related counters.
  * @get_eeprom_len: Read range of EEPROM addresses for validation of
  *     @get_eeprom and @set_eeprom requests.
  *     Returns 0 if device does not support EEPROM access.
@@ -652,6 +667,8 @@ struct ethtool_ops {
        u32     (*get_link)(struct net_device *);
        int     (*get_link_ext_state)(struct net_device *,
                                      struct ethtool_link_ext_state_info *);
+       void    (*get_link_ext_stats)(struct net_device *dev,
+                                     struct ethtool_link_ext_stats *stats);
        int     (*get_eeprom_len)(struct net_device *);
        int     (*get_eeprom)(struct net_device *,
                              struct ethtool_eeprom *, u8 *);

diff --git a/include/linux/phy.h b/include/linux/phy.h
index ddf6619..9a3752c 100644 (file)
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -600,6 +600,7 @@ struct macsec_ops;
  * @psec: Pointer to Power Sourcing Equipment control struct
  * @lock:  Mutex for serialization access to PHY
  * @state_queue: Work queue for state machine
+ * @link_down_events: Number of times link was lost
  * @shared: Pointer to private data shared by phys in one package
  * @priv: Pointer to driver private data
  *
@@ -723,6 +724,8 @@ struct phy_device {
 
        int pma_extable;
 
+       unsigned int link_down_events;
+
        void (*phy_link_change)(struct phy_device *phydev, bool up);
        void (*adjust_link)(struct net_device *dev);
 

diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
index bb57084..aaf7c69 100644 (file)
--- a/include/uapi/linux/ethtool_netlink.h
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -262,6 +262,7 @@ enum {
        ETHTOOL_A_LINKSTATE_SQI_MAX,            /* u32 */
        ETHTOOL_A_LINKSTATE_EXT_STATE,          /* u8 */
        ETHTOOL_A_LINKSTATE_EXT_SUBSTATE,       /* u8 */
+       ETHTOOL_A_LINKSTATE_EXT_DOWN_CNT,       /* u32 */
 
        /* add new constants above here */
        __ETHTOOL_A_LINKSTATE_CNT,

diff --git a/net/ethtool/linkstate.c b/net/ethtool/linkstate.c
index fb676f3..2158c17 100644 (file)
--- 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;
 }