On an I219 (pch_spt+) copper with jumbo MTU enabled, a link partner
reset (e.g. a switch reboot) can leave the PHY's pause advertisement
bits dropped. Nothing re-asserts them on link-up, so every renegotiation
resolves flow control to none. rx_crc_errors climb and traffic stalls until
the interface is manually reset. Observed on I219-LM (8086:15b7) at
MTU 9000 behind a switch that was power-cycled.
In the watchdog, detect a completed autonegotiation that resolved
to no flow control despite pause being requested and the pause bits
missing from the advertisement, and schedule reset_task to rebuild
the advertisement (as ethtool -r does). Remediation is limited to three
attempts, 30s apart, until the next link down.
Remediate via the existing reset path rather than re-asserting the
advertisement on link-up; a root-cause rework can follow in net-next.
Fixes: 79849ebc0e06 ("e1000e: initial support for i219")
Cc: [email protected]
Link: https://github.com/systemd/systemd/issues/25925
Assisted-by: LLM
Signed-off-by: Craig I. Hagan <[email protected]>
---
drivers/net/ethernet/intel/e1000e/e1000.h | 11 ++
drivers/net/ethernet/intel/e1000e/netdev.c | 132 +++++++++++++++++++++
2 files changed, 143 insertions(+)
diff --git a/drivers/net/ethernet/intel/e1000e/e1000.h
b/drivers/net/ethernet/intel/e1000e/e1000.h
index 63ebe0037..4353519d4 100644
--- a/drivers/net/ethernet/intel/e1000e/e1000.h
+++ b/drivers/net/ethernet/intel/e1000e/e1000.h
@@ -210,6 +210,17 @@ struct e1000_adapter {
/* track device up/down/testing state */
unsigned long state;
+ /* Flow-control advertisement-latch auto-recovery.
+ * These MUST persist across the reinit that remediation triggers
+ * (the reinit generates its own carrier-up), so they are NOT reset
+ * on link-up. The holdoff and per-episode attempt budget prevent a
+ * reset/flap storm against a partner that is still booting or that
+ * genuinely never advertises pause.
+ */
+ unsigned long fclatch_last_fix; /* jiffies of last remediation, 0=none
*/
+ u8 fclatch_attempts; /* attempts in the current link episode
*/
+ bool fclatch_gave_up; /* terminal for episode; re-armed on
link-down */
+
/* Interrupt Throttle Rate */
u32 itr;
u32 itr_setting;
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
b/drivers/net/ethernet/intel/e1000e/netdev.c
index 844f31ab3..28bd33335 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -38,6 +38,15 @@ static int debug = -1;
module_param(debug, int, 0);
MODULE_PARM_DESC(debug, "Debug level (0=none,...,16=all)");
+/* Flow-control advertisement-latch auto-recovery tunables. Fixed constants
+ * rather than user knobs: the values only need to be safe, not tunable.
+ * MAX_ATTEMPTS : autoneg-restart attempts per link episode before giving up
+ * HOLDOFF : minimum spacing between attempts; longer than a switch's
+ * autoneg settle so we do not fight a still-booting partner
+ */
+#define E1000E_FCLATCH_MAX_ATTEMPTS 3 /* autoneg-restarts per link
episode */
+#define E1000E_FCLATCH_HOLDOFF (30 * HZ) /* min spacing between
attempts */
+
static const struct e1000_info *e1000_info_tbl[] = {
[board_82571] = &e1000_82571_info,
[board_82572] = &e1000_82572_info,
@@ -5217,6 +5226,113 @@ static void e1000_watchdog(struct timer_list *t)
/* TODO: make this use queue_delayed_work() */
}
+/**
+ * e1000e_check_fc_latch - re-assert a dropped pause advertisement
+ * @adapter: board private structure
+ *
+ * On the I219/PCH family at jumbo MTU, an upstream switch reboot can bring the
+ * link back with the PHY's pause-advertisement bits dropped and flow control
+ * resolved to none, even when a pause mode was requested. The driver does not
+ * re-assert the advertisement on a plain link-up (e1000_phy_setup_autoneg()
+ * runs only during a full setup pass), so every later renegotiation resolves
+ * to none and the link does not recover on its own.
+ *
+ * Detect that state from a fresh PHY read and schedule a full reconfigure (the
+ * reset_task path, as ethtool -r uses) to rebuild the advertisement.
reset_task
+ * bounces the link and re-enters this check, so the attempt count is kept
+ * across the bounce rather than reset on link-up. Remediation stops after
three
+ * tries per link episode; the give-up state is re-armed only on a real
+ * link-down (peer/cable change), so a partner that never advertises pause is
+ * reset three times and then left alone until the link is re-established --
+ * it cannot flap indefinitely.
+ */
+static void e1000e_check_fc_latch(struct e1000_adapter *adapter)
+{
+ struct e1000_hw *hw = &adapter->hw;
+ struct net_device *netdev = adapter->netdev;
+ u16 bmsr = 0, adv = 0, expected;
+ unsigned long now;
+ int rv;
+
+ /* Skip while down/resetting or with a reset already pending. */
+ if (!netif_carrier_ok(netdev) ||
+ test_bit(__E1000_DOWN, &adapter->state) ||
+ test_bit(__E1000_RESETTING, &adapter->state) ||
+ (adapter->flags & FLAG_RESTART_NOW))
+ return;
+
+ /* Limited to I219/PCH copper at jumbo MTU, where the behavior is seen
+ * and the RX-side impact matters. Act only when a pause mode was
+ * requested but autoneg resolved none. Pause is only meaningful on a
+ * full-duplex link, so a half-duplex result legitimately carries no
+ * pause bits and must not be treated as the fault.
+ */
+ if (hw->phy.media_type != e1000_media_type_copper ||
+ hw->mac.type < e1000_pch_spt || /* pch_spt+ (I219 and
later) */
+ netdev->mtu <= ETH_DATA_LEN || /* jumbo only */
+ adapter->link_duplex != FULL_DUPLEX ||
+ !hw->mac.autoneg || !adapter->fc_autoneg ||
+ hw->fc.current_mode != e1000_fc_none)
+ return;
+ if (hw->fc.requested_mode != e1000_fc_full &&
+ hw->fc.requested_mode != e1000_fc_rx_pause &&
+ hw->fc.requested_mode != e1000_fc_tx_pause)
+ return;
+
+ /* Fresh, self-contained reads; act only on a good, autoneg-complete
read. */
+ rv = e1e_rphy(hw, MII_BMSR, &bmsr);
+ if (!rv)
+ rv = e1e_rphy(hw, MII_ADVERTISE, &adv);
+ if (rv || !(bmsr & BMSR_ANEGCOMPLETE))
+ return;
+
+ /* Pause bits we should be advertising for the requested mode (mirrors
+ * e1000_phy_setup_autoneg): full/rx use CAP|ASYM, tx uses ASYM only.
+ */
+ if (hw->fc.requested_mode == e1000_fc_tx_pause)
+ expected = ADVERTISE_PAUSE_ASYM;
+ else
+ expected = ADVERTISE_PAUSE_CAP | ADVERTISE_PAUSE_ASYM;
+
+ /* The advertisement should carry these bits; missing them while a pause
+ * mode was requested is the failure this recovers from.
+ */
+ if ((adv & expected) == expected)
+ return;
+
+ now = jiffies;
+
+ /* Give-up is terminal for this link episode; it is re-armed only on a
+ * real link-down (see the watchdog link-down path), i.e. when the peer
+ * or cabling actually changes -- not on a timer, which cannot tell a
+ * recovered switch from the same never-pause partner 60s later.
+ */
+ if (adapter->fclatch_gave_up)
+ return;
+ if (adapter->fclatch_last_fix &&
+ time_before(now, adapter->fclatch_last_fix +
E1000E_FCLATCH_HOLDOFF))
+ return; /* within holdoff */
+
+ if (adapter->fclatch_attempts >= E1000E_FCLATCH_MAX_ATTEMPTS) {
+ adapter->fclatch_gave_up = true;
+ e_warn("flow-control advertisement latch persists after %u
autoneg-restart attempts (adv=0x%04x, requested fc=%u); giving up until the
link goes down and back up\n",
+ adapter->fclatch_attempts, adv, hw->fc.requested_mode);
+ return;
+ }
+
+ adapter->fclatch_attempts++;
+ adapter->fclatch_last_fix = now;
+ e_warn("flow-control advertisement latch detected (adv=0x%04x missing
pause for requested fc=%u); forcing autoneg restart (attempt %u/%d)\n",
+ adv, hw->fc.requested_mode, adapter->fclatch_attempts,
+ E1000E_FCLATCH_MAX_ATTEMPTS);
+ /* Request the reset via FLAG_RESTART_NOW; the watchdog schedules
+ * reset_task on this flag just below the call site. The flag also
+ * tells reset_task this is intentional, suppressing its "Reset
+ * adapter unexpectedly" warning + register dump.
+ */
+ adapter->flags |= FLAG_RESTART_NOW;
+}
+
static void e1000_watchdog_task(struct work_struct *work)
{
struct e1000_adapter *adapter = container_of(work,
@@ -5353,6 +5469,17 @@ static void e1000_watchdog_task(struct work_struct *work)
netdev_info(netdev, "NIC Link is Down\n");
netif_carrier_off(netdev);
netif_stop_queue(netdev);
+
+ /* A real link-down ends the current fc-latch episode:
+ * re-arm remediation so the next link-up (e.g. the
+ * switch finishing its reboot) gets a fresh set of
+ * attempts. Our own reset_task bounce does not reach
+ * here (it goes through __E1000_DOWN/RESETTING), so
+ * this does not defeat the per-episode attempt cap.
+ */
+ adapter->fclatch_attempts = 0;
+ adapter->fclatch_gave_up = false;
+ adapter->fclatch_last_fix = 0;
if (!test_bit(__E1000_DOWN, &adapter->state))
mod_timer(&adapter->phy_info_timer,
round_jiffies(jiffies + 2 * HZ));
@@ -5384,6 +5511,11 @@ static void e1000_watchdog_task(struct work_struct *work)
adapter->gotc_old = adapter->stats.gotc;
spin_unlock(&adapter->stats64_lock);
+ /* Auto-recover from a latched pause advertisement (I219/PCH,
+ * jumbo) after an upstream switch reboot; see e1000e_check_fc_latch().
+ */
+ e1000e_check_fc_latch(adapter);
+
/* If the link is lost the controller stops DMA, but
* if there is queued Tx work it cannot be done. So
* reset the controller to flush the Tx packet buffers.
--
2.47.3
