linux-kernel - [PATCH iwl-next v3] igb: Retrieve Tx timestamp directly from interrupt for i210

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Message-Id: <20260205-igb_irq_ts-v3-1-2efc7bc4b885@linutronix.de>
Date: Thu, 05 Feb 2026 08:54:34 +0100
From: Kurt Kanzenbach <kurt@...utronix.de>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, 
 Przemek Kitszel <przemyslaw.kitszel@...el.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Vinicius Costa Gomes <vinicius.gomes@...el.com>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
 Paul Menzel <pmenzel@...gen.mpg.de>, 
 Vadim Fedorenko <vadim.fedorenko@...ux.dev>, 
 Miroslav Lichvar <mlichvar@...hat.com>, 
 Jacob Keller <jacob.e.keller@...el.com>, intel-wired-lan@...ts.osuosl.org, 
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Kurt Kanzenbach <kurt@...utronix.de>
Subject: [PATCH iwl-next v3] igb: Retrieve Tx timestamp directly from
 interrupt for i210

Retrieve Tx timestamp directly from interrupt handler for i210.

The current implementation uses schedule_work() which is executed by the
system work queue to retrieve Tx timestamps. This increases latency and can
lead to timeouts in case of heavy system load. i210 is often used in
industrial systems, where timestamp timeouts can be fatal.

Therefore, fetch the timestamp directly from the interrupt handler.

The work queue code stays for all other NICs supported by igb.

Tested on Intel i210 and i350.

Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
---
Changes in v3:
- Switch back to IRQ, but for i210 only
- Keep kworker for all other NICs like i350 (Miroslav)
- Link to v2: https://lore.kernel.org/r/20250822-igb_irq_ts-v2-1-1ac37078a7a4@linutronix.de

Changes in v2:
- Switch from IRQ to PTP aux worker due to NTP performance regression (Miroslav)
- Link to v1: https://lore.kernel.org/r/20250815-igb_irq_ts-v1-1-8c6fc0353422@linutronix.de
---
 drivers/net/ethernet/intel/igb/igb.h      |  1 +
 drivers/net/ethernet/intel/igb/igb_main.c |  5 ++++-
 drivers/net/ethernet/intel/igb/igb_ptp.c  | 22 ++++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 0fff1df81b7b..1de29670784e 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -776,6 +776,7 @@ int igb_ptp_hwtstamp_get(struct net_device *netdev,
 int igb_ptp_hwtstamp_set(struct net_device *netdev,
 			 struct kernel_hwtstamp_config *config,
 			 struct netlink_ext_ack *extack);
+void igb_ptp_tx_tstamp_event(struct igb_adapter *adapter);
 void igb_set_flag_queue_pairs(struct igb_adapter *, const u32);
 unsigned int igb_get_max_rss_queues(struct igb_adapter *);
 #ifdef CONFIG_IGB_HWMON
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index dbea37269d2c..d0d9245e6d72 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -7078,7 +7078,10 @@ static void igb_tsync_interrupt(struct igb_adapter *adapter)

 	if (tsicr & E1000_TSICR_TXTS) {
 		/* retrieve hardware timestamp */
-		schedule_work(&adapter->ptp_tx_work);
+		if (hw->mac.type == e1000_i210)
+			igb_ptp_tx_tstamp_event(adapter);
+		else
+			schedule_work(&adapter->ptp_tx_work);
 	}

 	if (tsicr & TSINTR_TT0)
diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index bd85d02ecadd..8c8f2b8615f7 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -796,6 +796,28 @@ static int igb_ptp_verify_pin(struct ptp_clock_info *ptp, unsigned int pin,
 	return 0;
 }

+/**
+ * igb_ptp_tx_tstamp_event
+ * @adapter: pointer to igb adapter
+ *
+ * This function checks the TSYNCTXCTL valid bit and stores the Tx hardware
+ * timestamp at the current skb.
+ **/
+void igb_ptp_tx_tstamp_event(struct igb_adapter *adapter)
+{
+	struct e1000_hw *hw = &adapter->hw;
+	u32 tsynctxctl;
+
+	if (!adapter->ptp_tx_skb)
+		return;
+
+	tsynctxctl = rd32(E1000_TSYNCTXCTL);
+	if (WARN_ON_ONCE(!(tsynctxctl & E1000_TSYNCTXCTL_VALID)))
+		return;
+
+	igb_ptp_tx_hwtstamp(adapter);
+}
+
 /**
  * igb_ptp_tx_work
  * @work: pointer to work struct

---
base-commit: e07d0d30939990da377672ef49ca09763b4fbc79
change-id: 20250813-igb_irq_ts-1aa77cc7b4cb

Best regards,
--  
Kurt Kanzenbach <kurt@...utronix.de>