On Tue, 2026-06-23 at 09:46 +0000, Kwapulinski, Piotr wrote:

quoted

-----Original Message-----
From: Intel-wired-lan <redacted> On Behalf Of Ding Meng via Intel-wired-lan
Sent: Monday, June 22, 2026 6:13 AM
To: Nguyen, Anthony L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw <przemyslaw.kitszel@intel.com>; andrew+netdev@lunn.ch; davem@davemloft.net; edumazet@google.com; kuba@kernel.org; pabeni@redhat.com; Kiszka, Jan <jan.kiszka@siemens.com>; Bezdeka, Florian <redacted>
Cc: intel-wired-lan@lists.osuosl.org; linux-kernel@vger.kernel.org; netdev@vger.kernel.org; meng.ding@siemens.com; wq.wang@siemens.com
Subject: [Intel-wired-lan] [PATCH net] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled

When CONFIG_NET_RX_BUSY_POLL is deactivated, fetching RX HW timestamps from the NIC no longer works as expected.

This occurs because disabling CONFIG_NET_RX_BUSY_POLL disables the SKB NAPI mapping in __skb_mark_napi_id(). Consequently, get_timestamp() fails to perform its driver lookup, and the igc driver's struct net_device_ops::ndo_get_tstamp is never invoked.

Instead, get_timestamp() falls back to use shhwtstamps(skb)->hwtstamp, a field that the driver has not populated.

Fix this by populating the hwtstamp field with the correct timestamp in the default timer when CONFIG_NET_RX_BUSY_POLL is disabled.

Fixes: 069b142f5819 ("igc: Add support for PTP .getcyclesx64()")
Co-developed-by: Florian Bezdeka <redacted>
Signed-off-by: Florian Bezdeka <redacted>
Signed-off-by: Ding Meng <redacted>
---
drivers/net/ethernet/intel/igc/igc_main.c | 38 ++++++++++++++++-------
1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 8ac16808023..1da8d7aa76d 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c

@@ -1992,7 +1992,26 @@ static struct sk_buff *igc_build_skb(struct igc_ring *rx_ring,

	return skb;
}

-static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,
+static void igc_construct_skb_timestamps(struct igc_adapter *adapter,
+					 struct sk_buff *skb,
+					 struct igc_xdp_buff *ctx)
+{
+	if (!ctx->rx_ts)
+		return;
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	skb_shinfo(skb)->tx_flags |= SKBTX_HW_TSTAMP_NETDEV;
+	skb_hwtstamps(skb)->netdev_data = ctx->rx_ts; #else
+	struct igc_inline_rx_tstamps *tstamps;

Please move at the top of the function and add:

That would trigger a "unused variable" warning in the
CONFIG_NET_RX_BUSY_POLL case.

Btw: I was really confused that the #else statement moved to the end of
the previous line. Might someone be using a wrongly configured mail
client here?

Florian

Reviewed-by: Piotr Kwapulinski <piotr.kwapulinski@intel.com

quoted

+
+	tstamps = ctx->rx_ts;
+	skb_hwtstamps(skb)->hwtstamp = igc_ptp_rx_pktstamp(adapter,
+							   tstamps->timer0);
+#endif
+}
+

[snip]