Re: [Intel-wired-lan] [PATCH net v2] igc: Fix RX HW timestamp reporting when NET_RX_BUSY_POLL is disabled

["Dahan, AvigailX" <avigailx.dahan@intel.com>]

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On 30/06/2026 14:15, Ding Meng via Intel-wired-lan wrote:
> 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>
> ---
> V2:
>    - update commit message(suggested by Paul Menzel):
>        add error log
>        explain why need to pass igc_adapter
>        add test case
>    - move variable declarations on top of the function
>    - Ccstable@vger.kernel.org
> V1:https://lore.kernel.org/intel-wired-lan/20260622041718.6106-1-meng.ding@siemens.com/
> ---
>   drivers/net/ethernet/intel/igc/igc_main.c | 41 ++++++++++++++++-------
>   1 file changed, 29 insertions(+), 12 deletions(-)
>
Tested-by: Avigail Dahan <avigailx.dahan@intel.com>

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