RE: [Intel-wired-lan] [PATCH net] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled

[Kwapulinski, Piotr]

>-----Original Message-----
>From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of Ding Meng via Intel-wired-lan
>Sent: Monday, June 22, 2026 6:13 AM
>To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel, Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>; andrew+netdev@xxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; Kiszka, Jan <jan.kiszka@xxxxxxxxxxx>; Bezdeka, Florian <florian.bezdeka@xxxxxxxxxxx>
>Cc: intel-wired-lan@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; meng.ding@xxxxxxxxxxx; wq.wang@xxxxxxxxxxx
>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 <florian.bezdeka@xxxxxxxxxxx>
>Signed-off-by: Florian Bezdeka <florian.bezdeka@xxxxxxxxxxx>
>Signed-off-by: Ding Meng <meng.ding@xxxxxxxxxxx>
>---
> 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:
Reviewed-by: Piotr Kwapulinski <piotr.kwapulinski@xxxxxxxxx

>+
>+	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
>
>