* [PATCH net 1/6] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled
[not found] <20261001222443.3500206-1-anthony.l.nguyen@intel.com>
@ 2026-10-01 22:24 ` Tony Nguyen
2026-10-08 1:57 ` Jakub Kicinski
0 siblings, 1 reply; 2+ messages in thread
From: Tony Nguyen @ 2026-10-01 22:24 UTC (permalink / raw)
To: davem, kuba, pabeni, edumazet, andrew+netdev, netdev
Cc: Ding Meng, anthony.l.nguyen, florian.bezdeka, p, tkusters,
jiayuan.chen, pulehui, vinicius.gomes, maciej.fijalkowski,
magnus.karlsson, ast, daniel, hawk, john.fastabend, sdf, bpf,
richardcochran, dima.ruinskiy, stable, Aleksandr Loktionov,
Piotr Kwapulinski
From: Ding Meng <meng.ding@siemens.com>
When CONFIG_NET_RX_BUSY_POLL is deactivated, fetching RX HW timestamps
from the NIC no longer works as expected, often resulting in incorrect
or negative values such as "HW raw -121948.050407424".
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. This results in incorrect
timestamps.
Fix this by populating the hwtstamp field with the correct timestamp
in the default timer when CONFIG_NET_RX_BUSY_POLL is disabled.
The "igc_adapter" is passed to igc_construct_skb() to enable
igc_ptp_rx_pktstamp() to access the necessary adapter details for
adjusting the timestamp.
Test case:
Disable CONFIG_NET_RX_BUSY_POLL.
Sender:
# tools/testing/selftests/net/timestamping en0 \
SOF_TIMESTAMPING_TX_HARDWARE PTPV2 IP_MULTICAST_LOOP
Receiver:
# tools/testing/selftests/net/timestamping en0 \
SOF_TIMESTAMPING_RX_HARDWARE SOF_TIMESTAMPING_RAW_HARDWARE PTPV2
Before patch, receiver prints
HW raw -121948.050407424
After patch, receiver prints
HW raw 1760648763.746974064
Fixes: 069b142f5819 ("igc: Add support for PTP .getcyclesx64()")
Cc: stable@vger.kernel.org
Co-developed-by: Florian Bezdeka <florian.bezdeka@siemens.com>
Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
Signed-off-by: Ding Meng <meng.ding@siemens.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Piotr Kwapulinski <piotr.kwapulinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
---
drivers/net/ethernet/intel/igc/igc_main.c | 41 ++++++++++++++++-------
1 file changed, 29 insertions(+), 12 deletions(-)
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 1fb5f3cbe93c..95f7747b347b 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -1989,7 +1989,29 @@ 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)
+{
+#ifndef CONFIG_NET_RX_BUSY_POLL
+ struct igc_inline_rx_tstamps *tstamps;
+#endif
+
+ if (!ctx->rx_ts)
+ return;
+
+#ifndef CONFIG_NET_RX_BUSY_POLL
+ tstamps = ctx->rx_ts;
+ skb_hwtstamps(skb)->hwtstamp = igc_ptp_rx_pktstamp(adapter,
+ tstamps->timer0);
+#else
+ skb_shinfo(skb)->tx_flags |= SKBTX_HW_TSTAMP_NETDEV;
+ skb_hwtstamps(skb)->netdev_data = ctx->rx_ts;
+#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)
{
@@ -2010,10 +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;
@@ -2683,7 +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) {
@@ -2735,7 +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;
@@ -2757,10 +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;
}
@@ -2772,7 +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);
--
2.47.1
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