-----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;

+
+	tstamps = ctx->rx_ts;
+	skb_hwtstamps(skb)->hwtstamp = igc_ptp_rx_pktstamp(adapter,
+							   tstamps->timer0);
+#endif
+}
+
+static struct sk_buff *igc_construct_skb(struct igc_adapter *adapter,
+					 struct igc_ring *rx_ring,
					 struct igc_rx_buffer *rx_buffer,
					 struct igc_xdp_buff *ctx)
{

@@ -2013,10 +2032,7 @@ static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,

	if (unlikely(!skb))
		return NULL;

-	if (ctx->rx_ts) {
-		skb_shinfo(skb)->tx_flags |= SKBTX_HW_TSTAMP_NETDEV;
-		skb_hwtstamps(skb)->netdev_data = ctx->rx_ts;
-	}
+	igc_construct_skb_timestamps(adapter, skb, ctx);

	/* Determine available headroom for copy */
	headlen = size;

@@ -2686,7 +2702,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)

		else if (ring_uses_build_skb(rx_ring))
			skb = igc_build_skb(rx_ring, rx_buffer, &ctx.xdp);
		else
-			skb = igc_construct_skb(rx_ring, rx_buffer, &ctx);
+			skb = igc_construct_skb(adapter, rx_ring, rx_buffer, &ctx);

		/* exit if we failed to retrieve a buffer */
		if (!xdp_res && !skb) {

@@ -2738,7 +2754,8 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)

	return total_packets;
}

-static struct sk_buff *igc_construct_skb_zc(struct igc_ring *ring,
+static struct sk_buff *igc_construct_skb_zc(struct igc_adapter *adapter,
+					    struct igc_ring *ring,
					    struct igc_xdp_buff *ctx)
{
	struct xdp_buff *xdp = &ctx->xdp;

@@ -2760,10 +2777,7 @@ static struct sk_buff *igc_construct_skb_zc(struct igc_ring *ring,

		__skb_pull(skb, metasize);
	}

-	if (ctx->rx_ts) {
-		skb_shinfo(skb)->tx_flags |= SKBTX_HW_TSTAMP_NETDEV;
-		skb_hwtstamps(skb)->netdev_data = ctx->rx_ts;
-	}
+	igc_construct_skb_timestamps(adapter, skb, ctx);

	return skb;
}

@@ -2775,7 +2789,7 @@ static void igc_dispatch_skb_zc(struct igc_q_vector *q_vector,

	struct igc_ring *ring = q_vector->rx.ring;
	struct sk_buff *skb;

-	skb = igc_construct_skb_zc(ring, ctx);
+	skb = igc_construct_skb_zc(q_vector->adapter, ring, ctx);
	if (!skb) {
		ring->rx_stats.alloc_failed++;
		set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, &ring->flags);

base-commit: 4549871118cf616eecdd2d939f78e3b9e1dddc48
--
2.47.3